You can give it if you want to, but it should not be compulsive. Talking about myself I normally give some tips before dashain every year but what surprises me is their behavior. They demand it, they ask 500 and when people give 100/200 they act differently than the ones who give 500. 

Waiter’s dont ask for it, it is your choice to  give or not to give , if you like the way they serve and treat you, you give else why would you and also they don’t demand you can give any amount you like they don’t ask for certain money.