It's got nothing to do with being a Professional, they've been wearing suits to games since they were little kids.
Putting a suit on to go to the rink is part of the pre-game routine same as taping sticks, etc.
They've been doing it forever isn't an actual reason to do something though. Taping sticks actually effects the game though you can't play without a taped stick.
Lots of workplaces that required wearing suits and ties don't any more.