"physical access = game over": well, there are levels of physical access, and this line of thinking is simply not good enough for smartphones and arguably laptops.

It should not be possible to break into a device simply by having it in your possession for a few minutes. Opening it up? Harder to protect against and therefore a lower priority. But some devices are glued shut and therefore more secure. (This security can be used against the user as well as by the user, but that's a whole other can of worms)