BART is full of white-collar people who use it to commute and to travel around the area (alongside all sorts of other kinds of people, as you would expect for a broadly used service).

Ridership collapsed in 2020 because of the pandemic, for obvious reasons, but it's hard to really blame that on the service itself, or the riders.

Ridership has been gradually recovering since then. Total trips are now up to something like 70% of 2019 levels, and continuing to rise. Number of unique riders is actually above the 2019 level now.

Maybe you haven't tried riding BART again within the past several years?

I left SF ~2021, but even in 2019 it was kind of in a death spiral. Hopefully it's better now, loved it back when I lived there. But still hear mixed reports from friends.