It's definitely why roads and parking are congested! People don't value access to roads properly, that's a big part of why driving became the default mode of transit.

The main reason why we should charge money for transit is because it makes it easier to kick off people who ruin it for everyone else. It's not important that transit covers its costs, it's important because requiring payment filters out people who don't value it.

It fucking sucks to be on a train with a homeless guy shouting threats into the air, or with a bunch of teenagers blasting music and intimidating other passengers. Once on the way back from work once, there was a guy watching porn at full volume in a car with children at the other end. Sure, you can say "call the police!" but it's much harder to place cops everywhere (purely expensive) than it is to just send out some ticket inspectors (who generally justify their own salaries).