Praising subs. Why?
1) The sub is good, and one wants to praise (to encourage and reward the author)
2) The sub is good, and by praising, you bump it (to the top to allow more people to enjoy it)
3) Reinforcing existing relationships
4) Bonding / creating new relationships
I don't think any of these things are necessarily bad things, but as Ed Hack implies, if it's all about 3 & 4, then part of the mission of the writer's room gets neglected.
Criticism needs to be more constructive to raise the level in this room.