You should know that not every athlete has great vision, some of them are also nearsighted as well. As you know, hockey is a conventional American sport, it doesn't matter if the player wear contact lenses. Some of them use contacts to see more clearly since framed glasses are not appropriate on the court, thus, contacts became plausible here.
I am not sure if all hockey players wear contact lenses while -playing. But you can wear it when you are playing. One of my friend who is very fond of playing hockey, but he is nearsighted. So, he often play hockey with his contact lenses. It is just OK. And he said he feel it better when wearing contact lenses for playing hockey.