Well Stan . . . the Brits certainly adopted driven shooting, didn't they? And that was invented by the French!
I think the purpose of a beavertail, as much as anything, is to sell shotguns to people who think they need something more substantial to grab onto than the barrels of a sxs. And, back in the day, quite a few American gun writers seemed to prefer BT. That also might explain why the Spanish maker Sarasqueta sent 7 different models of sxs to the American importer Stoeger back in 1961 . . . and all 7 of them are shown in the Stoeger Shooter's Bible with a beavertail. The Spanish didn't invent it either, but they understood the American market--or maybe Stoeger helped them understand it. Similarly, of the various models of sxs imported from SKB in Japan by Ithaca, only one (the 100) had a splinter. Miroku didn't make any of its Browning BSS guns for the American market with a splinter (other than the sidelock).
In short, the purpose of a beavertail is whatever the buyer thinks it is. And if he thinks he needs one, he will demonstrate that belief by buying a gun with a beavertail. If you want to know why . . . well, I guess you'd need to ask. Me, I think they're unnecessary, add weight, and just plain don't look as good. But there was very clearly a period of time, post-WWII, when the American public thought--for whatever reason, and probably not because they were worried about hot barrels (that being a fairly rare thing, especially on a hunting gun)--that beavertails belonged on sxs.
