Someone else can probably provide a more technical explanation, but basically all the benching done while powerlifting can often lead to very tight shoulders. Some "bench only" guys have such big and tight shoulders that they have to use the safety squat bar and giant cambered bar for their squats and even a trap bar to deadlift. Some guys end up squatting high-bar even though they would prefer to be squatting low-bar, because of a lack of shoulder flexibility. In general, a lot of powerlifters use a low-bar position to squat and that's a position that requires more flexibility in the shoulders.
I've noticed that a lot of the guys in the IPF keep their hands close together on the bar, even when using a low-bar position. Malanichev is a great example of a squatter who keeps his hands close together when squatting low-bar, despite his size.