But if you actually hunt elk and see a number of bulls taken with both repeatedly, you might understand why some choose a large 338.
Jeff
I've never shot an elk, but having observed the .338 bullets impact large brown bear and moose, I reached the same conclusion. The superior killing affect on really large animals is apparent with the .338s, compared to the 7mm and .308 bullets. Drop down to deer and black bear-sized animals, and the visible affects of the larger caliber bullets on game isn't really apparent, in my experience. In fact, a high velocity, smaller caliber bullet with often drop these mid-sized game animals faster than the larger caliber bullets traveling at slower velocity. Bullet speed with an expanding bullet seems to be the quickest killer of game weighing less than - say - ~400lbs in weight.
Those hunters experienced using .375, .416, and .458 caliber bullets on large Alaskan brown bear (900-1300lb) normally agree. The larger the caliber of the bullet, given equal sectional density, the more effective the kill. The .458 bullets from a .458 Win Mag will often deflate big brown bear at close range with a single solid hit to the chest.
With respect specifically to Long Range Hunting, the .338 is about the largest caliber offering with cartridges/bullets developed and commonly available to provide a good blend of high ballistic efficiency, offering high levels of retained down range velocity, energy, and lethality. All with tolerable recoil on a muzzle brake equipped rifle, or a suppressed rifle.