I don't remember any physical light switch that ever switch on or off by itself.
In an aircraft flying through turbulences I'd feel a lot more comfortable knowing that all switches are pyhsical. Try to use your smartphone while jogging...
Yeah they’re both switches, but size is incredibly important, and small mechanical devices are finicky and don’t produce nice clean digital output (that’s a lie that electronic engineers tell software engineers to keep things simple).
So yeah I’m sure you’ve never seen a light switch fail, but I bet you’ve seen a keyboard fail (especially if you’ve spent any time around a recent MacBook).
But I do agree with your point on using a touchscreen in turbulence. A counter point is that there are probably hundreds of controls or settings on a plane that you never touch during turbulence, possibly that you never touch in flight (like telling the flight computer how much cargo you’re carrying). Stuff like that is ideal for a touchscreen.