What I’ve noticed, is that metal halide lights are WAY less common than HPS or mercury vapor offerings for city-owned streets. I was never sure why. Metal halide puts out a much better light quality than HPS. MH is my favorite HID source and I wish they became standard on streets rather than HPS. I’m not a fan of clear mercury either but I even like those better than HPS.

I get that they don’t last as long as MV or HPS, but they look good and they actually are a white light. MH NEMA heads and MH coach style lanterns or UFO style posr tops also seem rare. Now, LED has taken over, and quality LEDs have even better light quality than MH. HPS made visibly on roads worse, and they also were a very warm color which wasn’t the most appropriate for a street.

The only time you’d find an MH cobra or post top was in cities that refused to use HPS (like Charleston, SC) or in upscale parts of a city. MH NEMA heads are pretty much non-existent, and only Cooper made them.

Shoeboxes, floodlights, decorative teardrop lights, and acorns seem to be an exception, as they’re all common in MH. Wall packs, bay lights, grow lights, and recessed cans don’t count as they’re not street lights.

Because they have lower efficiency and frequently explode at EOL. Just imagine maintaining thousands upon thousands
of MH fixtures. You will need many more spare parts for all the shattered refractors and dented reflectors.

Conventional probe start MH, especially when operated horizontally in a cobrahead tended to perform pretty bad compared to MV or HPS in terms of lamp life. There were some horizontal probe start lamps developed with curved arc tubes but they required special lampholders to allow for the proper orientation so they weren't that common.  Pulse start and CMH was a bit better but by that time most cities already converted to HPS and only opted to use those systems for upscale areas with higher budgets.

Toronto used quite a bit of MH in the older parts, a lot of streets used MH gumball luminaires ranging from 70w to 150w replacing incandescent gumballs in the mid 90s. They tended to use dual arc tube pulse start quartz lamps to get better lamp life and the gumballs had vertical lamps which worked better than cobraheads. There were some cobraheads and decorative MH luminaires with horizontal lamps, but they weren't as common as the gumballs.

I’d say @joseph_125’s statement pretty much summed up why MH wasn’t really used around here either. They were expensive to maintain and operate, so they were often reserved for special situations, such as downtowns, business districts, private developments etc. where aesthetics/better color rendition were desired.

Meanwhile had CMH come out much sooner for roadway use, we may have seen it more widespread as those did negate some of the disadvantages of conventional MH lamps, while offering better efficiency and improved color rendition. However it was simply too late, the writing was already on the wall because of LEDs.

Philips did try to sell them. The Citywhite or Cosmowhite or whatever they called it, can be swapped straight into SON compatible fixtures. My old neigborhood actually has one single HID lamp swapped into an entire neighborhood of HPS lamps. Why? No clue. Installer probably was one lamp short for a group relamp and reckoned no one will bother complaining about it. Alternatively one rolled into the box of tubular HPS lamps and it didn't get noticed until it was screwed in. The arc tube obviously looks very different to a SON arc tube, but maybe the guy thought 'Heh, (...) it, it is the final couple of years for this installation, let's see if anyone notices'.

I have two of them, and although it works on my HPS gear completely fine, i don't have an explosion-proof fixture.

We have and had so many SON fixtures, but i know only of the city of Groningen, on the Vestdijklaan, that actually seemed to use HID for public street lighting (except for an art project in Den Haag that used blue HID lights as the sole form of street lighting, giving the same impression as purpled out LEDs).
I delivered mail there, and i stared into those lanterns a lot of times, wondering about the cool white light and what kind of lamps those could've been, since LEDs were large panels, and SOX was never cool white. It was right at the start of the big ledification push, in 2020-2021. It was too bright and too much of a point source for LED so after a while i concluded MH
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Private lighting projects used HID slightly more often, buildings and walkways on commercial terrain were more often lit with HID or fluorescent than with HPS. If they haven't been removed by now, under the highway overpass where an Albert Heijn is located in Zaandijk (under the A8 highway) there are a bunch of HID flood lights lighting the underside of the overpass to make it more attractive to people shopping there.

EDIT: i think there actually is another HID installation still running in my city, either that or only a few SON's relamped with MH - Cornelis Bruijnzeelweg near Hornbach DIY store. I will verify next time i am there.

We did have some Philips CosmoPolis lamps migrate to the US. In fact one manufacturer, AEL, offered a 325 series luminaire that was equipped with compatible CMH components for them. The only city that would adopt CMH in a significant scale was Chicago, however they only used them in portions of the city and ultimately never did a total conversion. Pasadena, Calif. meanwhile did install a small group of CMH in their old town business district, but that was a one-off occasion.
 

MH lamps generally have shorter life than HPS and MV lamps.