I have a .280 because about 15 years ago I ran into a good deal on a lightly used Remington Custom KS Mountain Rifle in that caliber. It's light and accurate and I saw no reason for a .270 once I had that rifle.
This is how I ended up using the .280. I was in search of a .270 in a SS KS and after searching for some time (to no avail), stumbled into a .280. I figured "close enough".