Ticket prices are lower now than ever.

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.

Except now it'll be $540 while fuel is still low. It's going to go up even higher when fuel goes up.

I'm happy to subsidize, you know, low-income moms who need nutrition benefits. Why the heck should I subsidize people who pack too much on domestic trips?

What's your threshold for packing "too much"? Do you believe that everybody should be able to get by with an under-seat bag? Or are you pretending that the overhead bins are large enough for everyone to bring a standard piece of carry-on luggage?

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.