I don't want to be still handing out candy at 9pm, personally. And the 5 - 7 thing makes it easy to figure out how much candy-per-person to give; start out slow at 5, but if you still have a buttload by 6:45, you'd better start giving a lot per person. So I do like having a 2 hour scheduled time. But - even though I have two kids and a teen that go without adults, and one small kid that I go with briefly (he quickly gets cold or tired of walking or etc.) - I wouldn't mind if the whole thing was after dark. I remember waiting until it got dark to start when I was a kid, and don't get me started on how people have gotten ridiculous with "child safety" bs nowadays. And heck n my town, people have gotten so crazy with "halloween lights" (like Christmas lights, but orange or purple or pumpkin shaped @@) that it's not really dark after dark anyway.
This year it was snowing (first snow of the season) and hailing here on Halloween. So barely anyone trick-or-treated. (And yeah, people were bitching on the town facebook that it should be rescheduled. Ridiculous.) So my kids (who went out anyway, because I make them costumes that are actually appropriate for the weather) got a buttload of candy AND we had a buttload left over since no one came to take ours away.