They do, and the meters are way more advanced ones than they use on the houses. Utility and power companies keep track of how much power (momentary) and energy (cumulative over time) is going through any part of the grid, so they can know where are the big load concentrations, where upgrades are necessary, and where somebody is stealing

Having meters at a substation only and not on the houses won't let them know how much each house is using

Each user would have their own meter, and the only difference is that the meter is in a different location.

THATS WHAT I SAID!

Then you will have to have lots of individual wires going from the substation - which got several problems :

 - Not practical to implement

 - Require going to the substation to reset (or replace fuse) every little thing that trips

 - Prevent possibility of placing multiple homes on one "final" (high voltage to low voltage) transformer, so way more transformers to be installed near homes (so more resources to make and install all those transformers, and more losses - It is way easier to pick a transformer to work efficiently with some averaged out load than with many small loads of which few will be idle and few loaded to the max). Or if you want then to put the transformer in the substation, will require pulling low voltage line from the substation to the homes, which is very inefficient both in terms of energy losses and metal use for the cables

 - Require WAY more metal use for wires, as if each line goes to one home, there wont be possibility to undersize the main lines like they do with normal systems



Undersizing the main lines explained :

(For simplicity of explanation i am leaving the transformers out, so lets say everything is at the same voltage)

Lets say you have 10 houses wired with 100A each, powered all from 1 local power line. The line won't be sized for 1000A. It will be for 800A, and protected by a 800A fuse. This is possible because it virtually never happens that all of them load everything to the max at the same time

Then lets say there are 10 bunches of houses like that (so 10 800A local branch lines, each protected with 800A fuse), powered all from 1 main power line. The main won't be for 8000A. It will be for 6400A, and protected by 6400A fuse

....

What happens when in some place all the users do manage to switch on everything at once and overload their local line ?

Each of them "did nothing wrong" (did not overload his 100A limit), but together they blew the 800A fuse on the 800A line

But here lets remember, that the power generation capacity in the country (all power plants together) are not sufficient for the case that all the users will switch everything on at the same time. So something WILL have to trip, to protect the power plants. But that will cause a huge blackout. So it is better if something more localised trips, so only some of the users have blackout :

If the users of one bunch of houses exceeded their 800A, then we are sorry but 10 users will have blackout, but not everybody else

If they still didnt exceed their 800A, but 10 such bunches together exceed 6400A (think how unlikely it is that, now we need not 10 but 100 users by coincidence to take specific amount of power at the same time, and not too much either to not trip their local 800A first), then we are sorry but 100 users will have blackout, but not everybody else

....

If instead all those users are wired each woth 100A wire from the substation, then the amount of metal you use for those wires is same as would go for 100 x 100 = 10000A and not 6400A. And there goes all the metal you could save on the wires. (you still can fuse them in groups of 10 at 800A and those in groups of 10 at 6400A at the substation, so i am not bringing the stepped protection as an argument directly. But stepped protection is usually implemented at the places of branching and not centralised)

So one big power line is more practical.
Do these power factor devices stop power line internet networking from working?
It seems like it would, as the capacitor would muffle the signals.

I dont think it is practical to transfer "everyone's" internet on main power lines - There is more data to carry and more interference from everyone, thats quite contradicting things. I'd rather expect it to be carried by some more efficient means (optic fiber, ...) right up to somewhere very close to the user, and there injected into his branch of the power line

I'm thinking of those plug-in power line networking devices.
They also aren't very common here.

They are for short range home LAN, not capable of any more than that anyway

They are for short range home LAN, not capable of any more than that anyway

But would power factor correction devices on the same network (circuit breaker) impact the effectiveness of this type of networking?

The network is lost as farther apart the units are due to attenuation in the lines. The circuit breaker does not act as some sort of barrier for the network. Maybe there is some (more noticable than just wire) attenuation from the little coil in the breaker, maybe some more just from Phase and Neutral wires going apart inside the panel, hut nothing marks the end of the network

Generally, the power line cannot be treated as "just wires" for the frequency at which the data is. It becomes a Transmission Line, and you have to analyse how exactly the wave spreads through the specific wiring setup. Here many interesting things might happen - like simply open end on a branch of the right length (receptacle with nothing plugged into, ..) might appear as open for 50/60Hz (as expected) and as short circuit for the data. Yet if the branch to that receptacle was double the length it would appear as open for the data too. Triple the length as short again. And so on. Weird is it ? Thats because as wave, the signal reflects back from the open end and depending on the length to the open end and back, will be in Phase or in reverse Phase (so cancel out) the original signal

This and many other things happen at high frequencies, which you dont take into account at 50/60 Hz because the wavelength of 50/60 Hz is many times of magnitude longer than all the wiring in  the circuit, so all the circuit is in the same wave (in Phase) at any time

A PFC capacitor is in theory a short for high frequencies, but if it is on a branch of the right length it will appear as open and do nothing, and so on..

In reality a home circuit is complicated and non uniform (many branches with different cable types and different cross sections, with diferent things connected to) so it will never be a perfect communication link and never a complete short circuit either. It will be something inbetween, usually enough to get the data over inside the house. The adapters do some frequency hopping, so if at specific frequeny the link is bad, they will switch to another frequency (changing the wavelength and therefore the effect of each branch of the circuit on the link)

Sounds like those powerline networking adapters are relatively technologically advanced for being wired devices.

With the power lines, how they are arranged and so on, you can not count on any exact high frequency electrical properties.
It uses just the fact, some HF power will get through, even when greatly attenuated and with a lot of noise.
This means you need rather high transmitting power (some W's) to reach just few km with low communication speed.
The only reason to use these wires (over wireless radio) is you do not need an extra antenna, no need for any radio license and the fact  if the wires go there, some signal will do as well.

So for a regular internet connection it is rather useless (for longer distances than few meters within a house). But for the telemetric data like the smart meters or so, the few 10's of effective bits per second attainable data rates is sufficient.

That would be interesting, have digital meters use powerline networking for communication for energy usage.