It doesn't matter to them that you're on A) a diet, B) a budget or C) don't care for any of the appetizers, cocktails or shellfish, they just want you to help pay for theirs.
That's 'socialism'.
No one likes to be played for a chump so the next time you go out with these friends, you order every appetizer on the menu, a bottle of wine, filet minon and dessert, figuring at least this way, you'll get your fair share of what you're paying for.
Meanwhile, more folks keep joining you for lunch.
The lunch bill keeps escalating until you all go broke.
This is why socialism has never worked anywhere or any time its been tried.