And I think the reason is that AirBnB hosts have no incentive to improve anything. Because there's always another sucker. Who cares if city41 never stays again or if city41 tells everyone never to stay at Bob's AirBnB in Paradise, Nevada. Bob doesn't give a shit.
Bob only needs to convince one person to stay at a time. That's it. And then it's relatively easy money. Especially considering that while the lodger is staying, you don't have to do hardly anything. You spend a couple of hours cleaning up after they leave, and that's it.
Hotels need to convince everyone to stay. True, while they can eat the cost of one or two lodgers, they can't become known as a place with bad lodging. Hotels have operating costs in the millions. They have staff, they're turning over rooms daily, cleaning every room daily, industrial HVAC, a bar, a restaurant (or two), sometimes a tiny convenience store, concierge services.
Hotels are invested in you having an acceptable stay.
Not going to lie, when travelling, I tend to gravitate towards national chains for lodging. While I'll never find the true wonders of the whatever of living like a local or what people claim AirBnB provides, I'll never have a truly shitty lodging experience either. It's one of the areas where I'm not looking to have an adventure.