Two things can be true at once. Imo usually are.
The long range “fad” wont pass, because there is no down-side to it for the people not participating, and because the industry is making $ at it. Which is the entire point folks are making in why they might opt for a different cartridge today. Its both marketing hype and real benefit for shooters, even if its not relevant for most hunters.
Regardless, the answer to the OP’s question is driven by factory rifles and factory ammo. Handloading and customizing rifles is a low-enough % of the market that I dont think its relevant to the question. The market is being driven by the ability to do all those things off the shelf.
Yes, the entire premise of the question is FALSE, the 270 is very much alive and just as relevant and performs just as well today as it did 50 years ago. But its a hunting-only cartridge, whereas many of the newer options are perfectly legit hunting cartridges while also being top choices for competitive and recreational target shooting. The question could just as easily be “why dont I see 270win rifles at prs, NRL or fclass matches?”, and the answers would apply to this topic as well.
Also yes, other cartridges offer similar on-game performance, but also offer other benefits that require customization to achieve with a 270. It is entirely irrelevant if those things can be achieved in a 270 via handloading or a new barrel…the entire point is to be able to do it off the shelf because most people are using factory guns with factory ammo. The 6.8western and 277 fury may have resulted in the existance of 1:8” barrels and higher bc bullets for hand-loading, which is great…but come talk to us when we can buy our choice of any factory 270win rifle in 1:8” and factory loaded 270win ammo with 165+gr bullets in bulk for target shooting.
Also, also yes, hunters do not drive the ammo market. Shooters do, and that is not the same. Shooters ARE interested in the incremental benefit provided by higher bc bullets, lower recoil, etc that arent available off the shelf in a 270win. The proof is visible anywhere you look…
1) when is the last time you saw 200-round “value packs” of 270win ammo? I have 200rnd containers of budget 6.5cm ammo as we speak. Hunters writ large buy a box or three of rifle ammo per year. Shooters buy multiple flats at a time.
2) raise your hand if you’ve personally fired over 1000rounds of 270win ammo in the past 12 months? Guessing its not many people…but theres dozens just on this site that have fired that many and more in 6.5cm, 6cm, etc bolt action rifles. This is simply a measure of demand and what is driviing the market…it isnt hunting in the big picture, it is target shooting which is then trickling down to hunting.