Being awake when everyone else is asleep is ostracizing, disorienting, and depressing. It's not as much fun as you think, listening to people snore, even if you love them. It's actually one of the very few things that's MORE fun, or at least more tolerable, if you live alone, because you have no one lying next to you, snoozing peacefully in the arms of Morpheus, unpacking the cares of the day, hammering home the fact that you are broken, that your brain hates you, and that you are completely out of sync with the rhythm of the world.
And so you decide to get out of bed, because lying there will just make it worse. Maybe you'll get a little work done. HA. More fool you. Being awake when you should be asleep has one defining physical quality: you're out of sync with time, and that means you are FREEZING. (Terry Pratchett nails this in "Thief of Time.") I don't care if it's the middle of summer in Florida with no AC: you are shivering too hard to type accurately.
It should be mentioned here that part of the assumed glamor about being up when no one else is includes the idea that you'll meet someone. Maybe not in a romantic way, but that you'll have a deep conversation with someone you've never met before, baring your soul in the way you can only do in the middle of the night with a stranger that you'll never see again, some twisted Puritan version of Confession for the Damned. It seems so romantic, very Casablanca, that of all the hours of the night and out of all the diners in Seattle, you're sitting there, and so is that other person, and doesn't that mean that you and he have something in common, possibly even more so than you do (at least at this moment) with your lucky, lucky, sleeping partner?
No. Because literally no one is at their best in the middle of the night. Not you, not your promised conversational partner, not anyone. The reality of being up when no one else is is more like the jungle: everyone reverts to their basic lizard instincts, like that scene in Mean Girls. You have to physically watch yourself to make sure you don't start grunting and pointing as you hunch your cold body over the counter. And so you try to talk to the waitress, if you can and she has time, and eating greasy food just to have something to do, and re-reading a book you've already read a million times before, watching the hours tick by, wishing that you could have stayed there, with your partner, in the warm and cozy bed, where you thought you belonged.