If you take BART and Muni trains regularly you'll notice the crowd is very very different, with BART probably mostly being used by out-of-city commuters working

If you take BART and Muni trains regularly you'll notice the crowd is very very different, with BART probably mostly being used by out-of-city commuters working in the service industry and the occasional Berkley students, and MUNI servicing more SF residents. Most of the wealthy tech class avoid the BART like the plague, and it's easy to see why because a good 10-20% of the BART passengers are just homeless people roaming around the trains. So seeing as how rich people never use BART, it's easy to understand why they associate it with just undesirable people and a vessel for transporting them into the city.