@Road_Guy_Colin Generally, it's because teams are playing with 2 different sets of rules. The regular season and playoff hockey are two very different games, and sometimes a team or two just can't play that style of hockey.
@HabsOnReddit This is the exact problem of having two sets of rules in the game. No other sport puts the whistles away and lets them play in the playoffs. You play an entire regular season with a base set of rules that's thrown away come playoff time and someone is going to get hurt.