I understand wanting flexibility (when I choose Southwest, that's usually the main factor). But I don't understand how a "last minute trip" means holding on to the ticket until departure time. Even if you wait until the last minute, don't you have to stuff some things into a carry-on, drive to the airport, park, clear security, etc etc.? I can't imagine a scenario in which I wouldn't know at least 3 hours or so before departure time if I was going to actually use a ticket or not.

(having a backup reservation is the one scenario I did think of, but unless you're on another airline also, I think they've completely closed this loophole)