Butt why?

The big sign at the front of the bus that says "Please exit at the rear doors" is clearly too complex for most bus riders to understand.

How hard it it to understand that the whole bus riding process will go much smoother if you get off at the back while people get on at the front? It's very simple physics. Everytime you get off at the front, you slow down the whole bus trip for the rest of us by slowing down the people who are trying to get on. Why do you do this?

I think it comes down to how sexually repressed we still are. Do people really think that it will make them look bad if people see that they enjoy getting off at the back door?