I have a few questions about EOL protection:

-On some ballasts EOL protection kicks in if an arc can't strike within a few seconds, why is that?

-On some other ballasts, EOL protection takes a few minutes to kick in; the EOL tube will go EOL for a little bit, and then the ballast seems to do something and the tube kind of dies down until it's  either glowing very dimly or doing nothing, why is that?

-What exactly is the EOL protection circuit? Does it just simpily cut out a bad lamp?

-Why do some ballasts have/not have protection?