The 88-94 era sbc GM serp set-up has a bolt-in pulley for the purpose of a/c delete. Dorman has the part as well.
I guess you could keep a separate belt. A delete pulley, and pile of tools in the trunk along with all the other stuff... but that gets noisy and takes up space quick.
Besides, if your ac compressor locks up on a drive, would you rather sit on the side of the road doing all those modifications? Or just cut the belt off the a/c and continue on your way?
That's the advantage in the v-belt. You can have your alternator, your ac compressor, accessories fail
WHILE ON THE ROAD AWAY FROM HOME and still continue on your way either at least a good 30 miles minimum (did it in an 83 regal that lost its alternator) to safety without overheating and blowing your engine, or in the case of a/c indefinitely.
Sometimes you just don't want to sit on the side of the road, in the dark, or in an undesirable area, heck even just an unsafe high traffic area working under the hood swapping a bunch of parts or sit waiting for a tow.
That's the v-belt advantage.