Mule Deer has addressed this question/point in a general sense many times.
Money! But not in a bad way, in a capitalistic way. Stuff that generates revenue sticks around. Unlike the good members here, not everyone who is a hunter is a gun slut. In fact the best hunters I have met consider their rifles/shotguns as tools. "Wipe down the crescent wrench and put it up until needed". These guys get by with one or two rifles for a life time and generally use boring old cartridges that just work and are available where ammo is sold. I own a 280 and can, with confidence tell you the one thing that it tangibly does that a 270 does not, which is cost 50% more per box of ammo!
I felt that during the short and shorter craze the manufacturers through a whole bunch of stuff at the wall to see what would stick. Whatever people buy will stick around. Some of the cartridges that didn't stick may well have been superior but not enough so for people to wander from what already works and is readily available.
Truth here. I'm a gun guy, but my hunting rifle sits until general hunting (deer and antelope) season. I have other rifles that I shoot much more for other purposes. I bought a hundred rounds for this rifle ten years ago. It's a lifetime supply.
