Most shops have a belt sander with the disc sander at the side.
I'm betting only a fraction of the use of the belt sander involves that disc ditty. In all the shops I've seen, I don't think I've seen anyone use one, except a moldmaker who had two huge dedicated pedestal-type disc sanders, about a two-foot disc, counterweighted table and all, fabulous machines, forgot the name, has a "K" in it, iirc.
For the people who do use them, I"m curious as to how/why. It seems to me that their one inherent flaw is a sfpm that varies with radius -- never seemed like a good idea to me.
I use a belt sander all the time, and I think many cnc shops have one parked by each machine. I actually have 5, three pedestals, one sears benchtop, and a Walls horizontal only benchtop, a real workhorse, but with belt centering problems. All the pedestals are bustid, tho.... too lazy/incompetent to fix'em.... goodgawd..... I use the Sears 99% of the time.... go figger....