There has to be some interesting reason why the .380 and .45ACP didn't go that routeAgain, browning designed these cartridges for his automatic pistols. He did not design them for dual use in revolvers. Remember, this was cutting edge technology. I’m sure there were fudds who didn’t trust the newfangled auto pistols, and thought a revolver chambered for the “hot new load” would be the bees knees.
I have read that Browning preferred the semi-rim. Perhaps there was uncertainty that cartridges could be made uniformly enough to headspace on the case mouth, by the millions. Also, when you look at really old cartridges in these calibers, the bullet is pretty heavily crimped into the case.
In any case, the semi-rim does not cause problems in a properly designed magazine, unless the cartridge is so short that it permits it.