I became a licensed driver in Cali and have driven across most of the state for a couple of decades. The one universal thing I have noticed is this weird tailgating issue that you mention. I don’t notice it too much up in the mountains on two lane roads, driving alongside the coast. People seem to be smarter about not tailgating up there.

But everyone else, in every city I have lived in NoCal and SoCal, tailgates at high speeds on the freeway, in every single lane. And they tailgate on the street. I watched three cars tailgating one another in the middle lane when the fast lane was wide open the other day. They must’ve been going at least 90 because I was going 70 in the slower lanes, with someone on my tail as well.

I have come to the conclusion when someone is tailgating you for miles with the possibility to pass, either they like the speed you’re driving at and don’t want to get tailgated themselves, lol... or they are just bullying you to get YOU to change lanes and it becomes a battle of the ego.

When I was a teen driver and for most of my twenties, I used to get embroiled in those battles of will, which is very dangerous obviously.
Now I just put my hazard lights on which seems to do the trick to get them off my ass. This does work consistently every time for me. Just passing it along.