When I first started running I'd run mornings before uni - course I was getting up at 5am in order to get an hour's running in followed by shower, breakfast, etc prior to an 8am class.
No, I don't know why I did it either.
Now I prefer evenings; it was nice to run in sunshine at 9pm during summer, and now autumn's in full swing it's ever-so-slightly warmer in the evening. It's also because I've heard the same advice as others above regarding evening rather than morning being a better time to run.