public transportation

Here are some questions I have about the people who ride the " T" in Pittsburgh:

Why is it that the people who end up standing on the T are the ones who have no control over their balance?

Why do some people sit down, allow others to sit next to them, then get off one stop later?

Why do some people who seem content sitting in their seat, all of a sudden get up and change seats?

Why can't some people understand that the doors on the second car during rush hour do not open at every stop?