[WalterBright]

One reason not mentioned (or maybe it's only me):

If I've got bunch of problems, I'll work on the easiest ones first, saving the hardest for last. This clears my mind from the drag from the easier problems, and as a side effect I wind up committing more.

There's no particular correlation between how hard a problem is to solve vs how much time it takes to solve them. So hit the easy ones first and make your users happy!