I see plenty of guys running into opposition players, but rarely are they the kind that separate the man from the puck. It's rare that anyone other that Ovie or Wilson make the kind of hit that will make the opposition or its fans cringe, the way just about every hit Green takes makes me feel. Granted, the cumulative effect may take its toll, but the majority of the damage is going to come from 8 and 43 and I question whether that will be enough of a factor to alter the outcome of a series.
The cumulative effect WILL take its toll.
Separating the man from the puck is just one beneficial outcome of hitting.
Finishing your checks doesn't mean that will always happen. What you do is even if the guy releases the puck you hit him. You keep doing that and it wears that player down especially over the course of a series.
There is also the mental aspect. Finishing your checks will make opponents jittery with the puck and will lead to turnovers as they will be worried about bracing themselves for the incoming hit. This only happens if they know they are going to get hit. When you consistently finish your checks the other teams knows they are going to get hit.
Also another aspect...it takes one of their guys out of the play. Especially if its a pancake hit. Johansson did that to McQuaid just the other day. Orpik, Wilson and Ovie do this alot but other guys deliver now and then too. Still even if not a pancake hit it still takes a guy out of the play for a second or two. That can be big.