Monkeyleg,
I'm not a hunter, either, but the impression I've always gotten is that animals require more powerful cartridges because they don't realize what has happened to them, so they just stupidly keep going. Humans, of course, think "Ah! Oh man, I've got a big hole in my stomach it's bleeding please don't shoot me anymore!" and give up. And with humans, a quick kill is not so important as just surviving the encounter. A lower recoil cartridge helps you do that.