All these control variations can be trained around. I learned to flag my firing hand thumb away from the slide early on so slide mounted controls are no big deal.
I think the drive for frame safeties come from the 1911/2011 crowd and the popular grip people used to shoot one well (strong side thumb riding safety/close to the slide, web of firing hand centered in the beavertail).
I also think if more folks manipulated pistols off the front of the slide instead of the rear then many of the gripes about slide mounted controls would go away.
In case someone has not seen Langdon's take: