If you have top guys, you want them playing together and playing more shifts. Balancing lines tends to stifle offense. It's as likely to diminish the top guys as it is to boost the lesser players.
Colorado is going to roll Nathan MacKinnon and Mikko Rantanen as much as possible. Winnipeg wants Mark Scheifele, Blake Wheeler and Kyle Conner on the ice as much as possible.
If you get a game with a lot of penalties, then a coach basically plays three lines plus his power play and his penalty killers. The game has changed a bit, with some coaches leaning less on a checking line for matchups.
The Blues don't have superstars up front. They have balance. Berube could use Ryan O'Reilly's line as a matchup line and also feature a shutdown line with Oskar Sundqvist and Ivan Barbashev when his team was fully healthy. That turned the third line, an offensive-minded unit often featuring Robert Thomas, into more of a sheltered role with some offensive zone starts. So that scenario is about the closest to the Blues get to rolling four lines.