i've often thought the same for my Buckmark, for range fun it would be nice not having to use multiple mags just to rip thru some .22 ammo. Does seem strange that at least most (from what i understand anyway) .22 handguns do not come with higher cap mags, yet I can run a fs mag in my 9c (obviously others do that as well).
I'm sure someone will get creative and somehow make a deeper mag for these, just not sure how smooth and consistent something that is not from the factory would feed ammo