The 270 never caught on with long range because it burns a ton of slow fuel and is a barrel torch, at least in that line of work. Yes the 6 and 6.5-284 has its fans, but it has waned for the same reasons. A hunter can dial in his 270 without too many rounds and use the same barrel forever. A target shooter can roast a barrel in a season or two; it's similar to the 243 in this regard.
This simply isn't the reason.
For decades, NRA high power competition, aggregates at 200, 300, and 600 yards, required the use of the 30-06 cartridge. None others were allowed. So good boat tailed .308 diameter bullets were invented for match shooting, first the military's 173 grain bullet (originally developed to mazimize range by wlevating a machine gun instead of using artillery) and later Sierra's 168, 180, and 190 grain Match Kings.
1000 yard matches, however, had no cartridge limitations. Since good long range .308 caliber bullets were available, the logical step was to use faster 30 caliber cartridges, first the .300 H&H and later the .300 Winchester magnum.
A similar process in Europe yielded good boat tailed 6.5mm bullets of around 140 grains. So available long range target bullets were either 6.5mm or .308 inch. There were none in .25 or .270 caliber until much later.
A 14 grain difference in powder weight means abaloutely nothing, just as when .30 calibers were required for 1000 yard matches, the difference in capacity between a 30-06 and a .300 Magnum meant nothing.
Don't blame me. I voted for Trump.
Democrats would burn this country to the ground, if they could rule over the ashes.
