There are numerous entirely private systems that require such subsidy; are you claiming that any amount of subsidy for others' habits is objectionable (i.e. the libertarian hardline)? Or are you making some other point?
Poorer people can opt out of checking luggage in order to make that visit to a dying relative possible.
Everyone here forgets what it was like when a domestic flight cost the equivalent of $600 - which is out of reach for a lot of people.
Charging for luggage and dining separate from the ticket makes that possible, in part.
Either way, it's still possible to check smaller pieces of luggage, and if most passengers could do that economically then loading and unloading the plane would be a lot quicker, saving the airlines non-trivial costs.
From what you said it's abit like saying that you don't want to subsidize the police via your taxes because you never use them.
As to subsidies: you usually can't control whether you need the police or not. You generally can control how much you pack. My wife and I didn't even pack a check-in on when we took the kid to Disney World recently. Why should I pay more for people who have to have … whatever the hell it is that people pack in a checked bag for a domestic flight.
This basically forces me (who never checks anything) to subsidize your (I assume) traveling habits.