A relaxation of police enforcement would likely result in driving behavior change, but it would be hard for us to quantify. Could be the result of increased immigration from countries with different driving attitudes. Could be changes to drivers ed. Could be a lot of things. Most likely it's our perception that has changed as we've gotten older.
I doubt it's cyclist who get in their cars and forget they can't run red lights though. I run reds on my bike because it's safer than waiting at an intersection (this is a demonstrable fact, before anyone replies how much they hate me and my kind or how unfair or yada yada). What I don't do is carry that behavior over when I'm driving a car. I'm in a completely different mode.
>note: I'm seeing egregious traffic violations by cars every time I drive now which was not true say 10yrs ago. Don't know what changed
More cars on the road?
In my opinion if there's one traffic law to abide, it's that. Not signaling, speeding, etc are relatively harmless compared to running red lights. It's very rare to see anyone do that in here (Northern Europe) and I think the fines for that are also the largest among related fines.
it could be
(1) got used to it on a bike so repeating in car
(2) saw cyclists get away with it so decided might as well do the same
(3) unrelated reason
note: I'm seeing egregious traffic violations by cars every time I drive now which was not true say 10yrs ago. Don't know what changed
as a cyclist I'd love to see Netherlands level of bicycle support in more cities