I think it is the product of European handgun thinking. They used to mill grooves in the grip strap and fit shoulder stocks to lugers, broomstick mausers, and the HK VP70. sort of carbinizing of the handgun. Only a short step from there to putting rear sights on them that take up 1/3 of the slide. Odd folk. Here in the new world we chamber handguns for rifle cartridges and slap scopes on them, but we still hold them in our hands just like Colonel Colt told us to.