It's the fact you are on public transportation -- when you give the underclass the same access to places (bus, Wal-Mart, etc.) as normal people, you tend to zero in on their wacky behavior.
When I commuted daily to/from home while attending college it seemed there was a crazy-person story I could tell every day. However, with time, I have forgotten most of my encounters. What really sticks out are two instances.
1) Homeless/ghetto trash peeing on the side of buildings that were designated historical landmarks.
2) Seeing these panhandlers work in shifts at a nearby McDonalds...