I think the bigger limitation with big bore sniping equipment or extra-long range sniping in the past, with rifles made from .50 BMG barrels or anti-tank rifles was the relative scarcity of optical equipment. To an extent, that was even true of rifle caliber sniping equipment used by armies. To some outfit doing experiments and trying to put something together in the field (I'm speaking of Korea and earlier), coming up with a good scope to match the extended range (which was the whole point) of the rifle would have been a challenge.
It's also the sort of thing that lends itself to a stable front line.