260 pretty much nailed it.

I can't help but believe there's something of a generational thing going on as well, although not all users of the new cartridges are smooth bottomed babes. When I was a young man the 308, 243 and other cartridges based on the 308 case, the Winchester magnums and maybe a few others were the new, hot items, although the old '06 and 270 never really lost favor. The 7mm Express Remington was making a feeble attempt to replace the 270 and the 7 Mag wasn't far down the road. The myth of short action superiority was being bandied about as well. Fine cartridges like the 7 X 57 Nitrox mentioned, the 300 Savage, 257 Roberts and the even better 8 X 57 were falling into dim memories. Don't even mention the fine, old big bore, BP cartridges or the lowly 30-30 or any of the many, unknown on these shores, European cartridges from between the wars that are superior to most even today. The 7mm Express Remington, (280 Rem.), from 1955-57 was no more than a near duplicate of the 7 X 64 Brenneke from....wait for it....1917. 20 years ago the 6.5 caliber was just being "discovered" by American shooters, as if they developed the caliber. Tell me again, how old is the Swede and the 6.5 X 54 Mannlicher/Schoenauer, 6.5 X 57....and other 6.5 cartridges?

Point being, as young men my generation looked to the newer stuff before we grew up and, if you learned anything, realized, much as 260 said, there's precious little really new. As 260 also mentioned, the biggest development over the last 30 years has been in propellants.

The vast majority of popular cartridges are essentially based on two cases, the 8 X 57 and the 375 H&H. One from 1888 and the other from 1912.

Fast forward 50 years from when I was a young man just going into the Air Force and you can get loaded ammo for cartridges declared extinct when I was a young man...at least you could before the Fauci Flu. It would appear not everyone is sucked in to what amounts to excellent marketing and development.