You are right they don't need to be, but from a building code perspective you can't bury the controller behind a wall. You have to make them accessible behind some kind of a wall plate so for aesthetics reasons people will likely end up putting switches there anyways.
I think the better option is, as you said, have all switches be wireless, and somewhere like a basement and have a bunch of 'controllers' to tell it to switch on or off.
That's true if your switches are talking to a 20A relay and flipping the circuit on and off. If all you have is a switch sending a radio signal to a lightbulb, then you no longer have a controller that needs to be accessible. Just the switches and various "internet of things" devices that are always plugged into always-on line power. That's what Thread is for.
The one thing I wonder about is replacing lightbulbs when they fail. It's a good safety practice to kill the circuit when you're doing it, and without a hardwired switch you'll have to do that at the breaker now. On the other hand, if you're buying fancy wireless LED bulbs, they'd damn well better last longer than an incandescent A19.
I think the better option is, as you said, have all switches be wireless, and somewhere like a basement and have a bunch of 'controllers' to tell it to switch on or off.