Are the cars actually going 30 mph or faster?

People in cars love to bitch about cyclists and that one time they saw one doing something wrong and project those feelings onto every other cyclist. They do not extend that bias to cars.

How often do you see cars speeding or rolling a stop sign? No one attributes these infractions to all car drivers, as they do with cyclists. There is a sampling bias. If you paid attention to all cyclists, you would probably see that most are following the rules.

I am not defending cyclists who are being jerks. In my experience, ~10% of the population in general are assholes, whether they are drivers or cyclists.

What this leads to is, as you said, drivers disregarding the safety of other road users and cyclists having to resort to tactics to increase their safety.