No offense, but I just don't buy this theory. Getting a few extra penalties is in no way a good enough return for putting yourself in a vulnerable position and risk getting a serious injury.
It ain't about getting a few extra penalties, it's about not getting hit at all. There's an unspoken trust amongst the NHL brethren that this line won't be crossed. You're probably so young that it looks normal to you that a defenseman facing the boards is almost never hit. There was a time when the defenseman who did this would have been drilled into the boards and the prevailing mindset had been that it was the player's fault for making himself vulnerable.
A similar evolution is happening with headshots and blindside hits. You may remember when having your head down searching for the puck at your feet then getting clocked in the open ice was considered legal as long as the hit wasn't led with an elbow.
Some more examples that has seen hockey change how it's played:
-Freezing the puck along the boards. Players used their size and strength to intentionally stop the motion of the puck along the boards to force faceoffs and line changes. Some players specialized in this as a tactic such as Walt McKechnie.
-Falling on or smothering the puck by defensemen. This was a common tactic to stop the play. Hall of Famers like Brad Park and Borje Salming were great at this.
-Holding by defensemen. When a defenseman hit and knocked a player off the puck along the boards, the referees allowed him to hold the player for something as long 5 seconds before having to release the player. Larry Robinson was a master of this.
-Shooting the puck over the glass. Untalented defensemen when in trouble in their own end would simply fire the puck into the crowd under the guise of "clearing the puck".
-Defensemen crosschecking/slashing/holding players in front of the goal. Few rules were enforced once a forward decided to park himself in front of the goal. Defensemen could hack and slash and grab and pull and crosscheck without getting a penalty. Crossing the line would involve crosschecking in the back of the head or breaking your stick on the player. If a player was good at withstanding this punishment, he was considered very useful.
