Don't know for sure, but I'd bet it goes back to the days when 1911's were the sidearm of choice for the military. Probably something to do with field maintenance/repair.
Very informative. Thank you!The whole idea was to ease the dis-assembly as Islander surmises. It does go back to the weapons trials of the very early 1900's. The military requirement was that the weapon could be dis-assembled, in the field, with a minimum of tools and that major components, like the main spring, could be replaced, without further deactivation of the rest of the weapon. That is, broken springs could be replaced and the weapon put back into action in the fastest possible time. Removing the grip panels would have required another tool and more time. If you compare pictures of the 1911 to it's predecessor, the M1900, you can see how much easier it is to dis--assemble the 1911.