I agree in general. Its a junk stat.
However, PIM becomes relevant stat when there are like, 200+ of them. Even the hook-iest, board-iest, interference-iest players in the league would be hard pressed to get 100 penalties, 2 minutes at a time. But when you've got a whole whack of 5 for fightings thrown in there, it adds up. If you see a player with 200 PIM and 30 points, you know at a glance he drops the mitts and puts a few away as well.
*shrug*