At first I wanted to write a comment about how cars and sex are apparently very well linked. Upon thinking it over once more, it appears that the real link to sex is privacy, which is of course obvious. Thinking over it once more, we're brought back to the real selling point of cars: total privacy. Public transport is on paper really good, but it is totally devoid of privacy - which means that it is bad in reality. In other more provocative words, public transportation is bad because you can't have sex on the bus

Public transport porn is actually a big thing in the Czech Republic, at least according to my bookmark collection.