Tipping is totally optional.
No it isn’t.
http://www.theyeshivaworld.com/coffeeroom/topic/tipping-waiter#post-687480
Maybe if kosher prices weren’t too high, people would have more money to tip. Stick to your job.
If you can’t afford the tip, don’t go to a restaurant. The price of kosher food in no way justifies withholding the waiters their due.