Why cars?

There is an expectation of privacy in a car that a public transit does not afford.

This is why people will own/drive cars even contrary to every cost benefit analysis in favor of public transit.

Unless the people championing public transit make privacy unpalateable or the net benefit of public transit much higher than privacy, cars are here to stay.

This could be done by emphasizing the camaraderie of traveling daily with known commuters. There are numerous stories of people who take local trains in India becoming close friends with other daily commuters. Given a choice, such folks would prefer the hustle bustle and sheer public-ness of public transit over the antiseptic silence of a car.

Public transit has to be presented as an adventure - you never know what you're going to get...maybe have a website where people laugh about the crazy stuff that happens on trains.

You can't beat cars on cost or intangibles like environmental benefits. Public transit can only win if people are willing to trade privacy for serendipity and adventure.