Coyote,
Thanks for your comment and question. Whilst respecting your view, I hold the contrary view and have done so for more year (decades) than I care to admit. I believe the popularity of the .270 (Win and WSM) is due to the inherent capabilities of the caliber and that the late great Jack O'Connor just wrote about them.
Having said that we are all reach our destination through different routes but it is the route that is colored by our experiences. For me the .270 Win was my second center-fire rifle back in the 70s (that's 1970s). Yes, I grew up on the writings of O'Connor and others, Keith, et al. But the 270 just impressed me with its ballistics. This rifle was based on a Mauser 98 and it shot sensationally and had power to spare for the hunting I'd do here. Hence the .270 Win became an instant favorite of mine.
Additionally I believe that the awesome capabilities of the .270 Win was extended with the introduction (in the 80s) of the 140 gr SPBT bullets. This bullet can be loaded to around 3,000 fps and gives almost as flat a trajectory as the famed 130 gr load but had (for all ranges past 100 yards) the retained energy of the 150 gr load. In the words of John Wootters (of Petersens publications),
that's some compromise. The Hornady 140 gr interlock and SST with a BC of close to .5 is a favorite of mine.
In recent years I realized I had not had a 270 in my gun safe for 20 years and set about rectifying that. Being a traditionalist and liking classic rifles I found Winchester pre 64 M70 fwt in that caliber (I already had an identical rifle on .308 Win) on Gunsamerica and did the deal (and organized it's importation to Australia). The rest is history.
I have never been a 7mm fan and have only ever had a 7x57 (Ruger M77) for a while but sold it. I guess the 270 (launched in 1925) just had the jump on the 280 (lunched in 1957, I think). By the time the 280 was released the 270 had too great a hold amongst hunters (bit like the VSH and the Beta video recorders). The other issue, as Craig Boddington has pointed out in his writing, is the caliber jump (a mere .007") is just not significant enough and there is the great 30-06 if you want to go a bit larger, for the 180 gr plus bullets with really great penetration. I think this is my next purchase a Winchester pre 64 M70 fwt in 30-06), but that's another story. We are talking here about sheep/mountain rifles. Rifles that don't need the great penetration of some of the 7mm (and .30 cal 180 gr) bullets, but need to be flat shooting and light. This is what the 270 does best, in my view.
I understand that the 270 is the best selling of the WSMs. The 7mm WSM is not listed in Winchester Australia's product list for any of the Winchester or Browning rifles. Also Chuck Hawkes published a list of the most popular calibres,
Readers Choice Rifle Cartridges. You will notice the .270 Win is No 3 whereas the .280 Rem does not appear.
Enjoy your hunting.