I think "car culture" is usually a good explanation for big picture decisions for transportation -- where society invests, how the government develops transportation-related policies, what people will protest locally against -- but a poor explanation for why people make day to day transportation decisions.
Pretty much anytime you see people hardly using public transit (or biking or walking) in an area, you can zoom in and discover that, shocker of shockers, it really sucks in one or more ways. People are mostly pretty rational when it comes to those day-to-day decisions, I think. Yes, it may seem silly that people will drive their huge truck to their office job a mere mile and a half away, but if you zoom in, you find that even their residential neighborhood has huge, wide streets that people speed around in, making biking feel uncomfortable and dangerous. And when everyone else has huge trucks going fast, being in a huge truck does make you feel quite a bit safer.
Another example, my hometown of the South SF bay area has excellent weather for biking, and the more populated areas are largely flat*, but biking there is still uncommon, and if you try to do so yourself you quickly discover why.
It's largely unpleasant and very dangerous-feeling, with fragmented, quarter-assed infrastructure that often seems designed to try and kill you. Who the hell feels comfortable biking on painted bike lanes on Lawrence Expressway next to 50+ mph traffic, I'll never know. And what little infrastructure there is often randomly disappears, like bike lanes that just sort of curve into the sidewalk (and not even a sloped edge, so I'm not sure what they expect you to do there). I personally got hit twice by cars the last year before I moved to Munich, including once when my son was on my bike (police came out, but they didn't even bother ticketing the driver who t-boned by rear wheel, of course).
* Yes, obviously there are hills around the valley, but most of the people and stuff is in the flat parts