Anybody can fill any aircraft at any time of day. The question is pricing and that is why all that matters to a carrier is PRASM.

Is there anybody here who seriously wants a system where 1/24th of the flights depart every hour and the convenient flights triple in price while the 03:00 shuttle to BOS goes out for 1/3 the pre-allocation price?

The large corporate accounts which keep commercial aviation alive, book for business convenience and then price. You really want to send someone making $500K+ out on a flight at 3:00 AM so he loses two days of work when he can fly TATL or TCON with no appreciable productive time lost?

This isn't the first time someone has raised the issue. The answer remains the same. It is naive and not thought through. Makes zero economic sense and won't happen.