Yes, it would be like the backup NFL quarterback standing with a clipboard next to the head coach learning and then working hard to become the starter next year. Or a tenth man on a NBA squad sitting on the bench and working towards a starting role next year. Both of the above cheering on their "TEAM" and enjoying the success or comforting their team mates in the times of rough going.
You are correct...why in the world would we expect the other three Mosconi Cup non playing team members to do that!
Wedge
A backup qb, tenth man, backup goalie etc has an actual role on a team, they can replace a starter who is injured or is playing badly, they are not part of a team just to be a cheerleader.
I think it was a dumb idea from the beginning, maybe just a way for Mark to name the 5, while at the same time not "really cutting" anyone from the team.
What would have happened when one, two or three of the 5 starts playing really badly or even makes just one mistake at a crucial time? With the 3 extras in the background, everyone would have been looking over their shoulders. It would have just been awkward.