A. At least he's working and not sitting out front with a sign begging for money
B. He could have been retarded, hence the slow service. This does beg the question as to why he was working the register, but certainly isn't out of the realm of possibility. My mother works for a company that helps retarded adults get jobs in their communities.
C. Maybe he *had* a good job but got the shaft and this is the only thing he can get to make ends meet right now. Certainly not an uncommon problem these days....
D. This is far-fetched, but I did hear a story once about a guy who was a multi-millionaire but was so bored he got a part-time job as a pizza delivery guy just to have something to do with his spare time.
The moral of the story? Don't be a superior asshole and judge a book by it's cover.