It all has to do with investment. LA has one of the largest metro systems and a million people use it a day. 60% of NYC commuters use public transport. In cities that build and improve transport, it gets used. It has nothing to do with culture but rather what is actually built.

It also doesn't help that transit agencies in smaller cities have been degenerate. Their answer for declines in ridership is to consolidate and cut service, not improve the network, which leads to more decline, and more consolidation, until you end up with a place like many commenters in this thread where 1 bus comes every hour, usually following the path of a former streetcar right of way that was ripped out by monied interests 70 years ago.