That’s because there’s a weirdly narrow subset of our population that have both experience with public transportation being available, and it being nice.
If your only experience with public transit was a slow, infrequent and unreliable bus that reeked of piss and came by once every two hours with no way to know if it’s running late or cancelled, you’d also come to the conclusion that a car was more convenient.

It’s one of those self fulfilling prophecy things. People expect public transportation to be awful, so they don’t use it, so usage numbers drop making sure funding gets cut further.