Three examples of where I've tipped in a lounge:
1. I don't eat meat with breakfast and the lounge has scrambled eggs mixed with meat. The staff offers to go to the restaurant and bring up a plate of meatless eggs.
2. I want something that the restaurant has but not the lounge, for example side of avocado, almond/soy milk, etc., and the staff goes to get it.
3. I want to work in the Lounge (possibly with colleagues) for several hours and staff brings water, coffee, etc.