Why?

Why on earth do people put up with doing this every day? (if they have an alternative choice, of course - I've got a colleague who lives within 2 minutes' walk of a train station, who drives through the bypass traffic every day he's in the office, and consistently complains about how bad it is). 

I think this is only the third time I've driven to work this year - already looking forward to next week's commute being back on the train!