Counter:
- Carry-ons can be objectively better for passengers.
- Go straight to your gate, no check-in drop-off
- No angst about lost luggage
- No interminable waiting at the luggage carousel
- Less TSA pawing through and stealing your stuff
- For many trips, a carry-on is all you need
- Carry-ons are cheaper for airlines.
- Carry-ons require no handlers to transport or physically stack luggage
- Carry-ons are categorically lighter and use less space than checked bags, translating to less fuel
2b could be mitigated by checking only carry-on-sized luggage; basically a smaller luggage-size limit.
I traveled for business for years, and got used to traveling only in a carry-on. My GRo (the best luggage ever built, and which you can no longer but) always fit into a single overhead space. I could pack underwear and several business shirts, toiletries, a pair of (compressable) casual shores, and wear my suit, and still have room left for a pair of jeans. It was a stretch to go for two work weeks, but I could do it. One week was no inconvenience at all. Now even when I travel for pleasure, unless it's a two week vacation I still only pack a carry-on.
That said: I'm a man, and women in corporate environments - unfairly - often feel obligated to pack more clothes: multiple pairs of shoes, multiple outfits, more cosmetics, etc. It is generally easier for a man to stretch a suit by altering only shirts and ties. Even so, my wife will also pack only a carry-on if the trip is 5-days or less. Even though the company pays for baggage fees, it's a worse customer experience at both ends of the trip to check a bag, and I don't think there's much airlines could do about that. It's a straightforward logistical problem.
Except for long, or specialty, trips (e.g, skiing, backpacking), carry-ons for us are subjectively, but uncontestedly, superior. Airlines reversing the fee schedule would be categorically worse for us, enough that we'd switch our frequent flier programs over it.