Maybe the thousands of hunting magazine articles, advertisements from manufacturers of rifles and bullets, TV shows extolling the virtues of new flatter shooting and harder hitting calibers has made an impression. Following that with an internet full of stories of bullets having to break shoulders at off angles from 400 yards to get that bull of a lifetime and that new magnum sounds like a necessary expenditure.
As a teenager I bought my 7mm Remington Magnum because the Physician who owned all the cool guns and shot at my uncles place used one for elk and sheep. My fathers 30-06 was just so boring by comparison.
But it could be the same reason we by sports cars, high performance optics, computers, clothing, tools, golf clubs, BBQs and everything else under the sun. Who doesn't want the best most efficient gear for their sports and activities.
People plunk down hundreds of dollars for girls softball bats so why wouldn't you get a bigger badder rifle for an animal 4 times the size of your local whitetail.
Some good reasons are that when distances are spread out triple what an Eastern hunter is used to shooting it is nice to have a flatter trajectory to keep required thinking about trajectory to a minimum. If all you need to think about is "center of the lungs right behind the shoulder" you are more likely to be more effective than thinking about drop calculations.
