Aside from the fact that most of us are night owls, it's probably more hotel logistics than anything.  You pretty much have to be at the same place for at least 2 days, and then beat the cleaning staff away to have the place to yourself for the morning.  ((FOR THE LAST TIME, I DON'T NEED MORE TOWELS!!!!))

Personally, I'm down for whatever time of day as long as I have a place to play.  My preference, however, is to start in the early evening, like 6-8 pm... It's the end of the day, so I don't have to worry about scheduling stuff, but still early enough that I'm not sleepy.  And if it happens to carry over until the wee hours of the morning, the so be it!

--Juliane