Sometimes. But if I'm flying out to somewhere at 6am, the alternative is often that I'd just be spending the night in my own bed. Now, to be honest, I'm sometimes fine with heading down somewhere the day before and having a relaxing evening at my destination. But that may not be ideal for people with families and isn't really justified from a business standpoint.

Agreed, if there were sleeper trains available. But finding a sleeper trains from A to B is much harder than finding a plane from A to B.