Servers have to "tip out" a certain amount of the money earned per table to the rest of the restaurant. Hostesses, bussers, barbacks, etc will get a tip out. In other words, even if you don't tip your server, they still have to pay the rest of the staff.

Tipping a percent IS stupid and tipping culture should change, but I think if you're going out and can't afford to tip at least 15% of what you're paying, then that's just not nice to the servers and you shouldn't go out if you can't afford the extra 15%. Even though tipping is "wrong," it's still the nice, courteous thing to do. Being a server is a really hard job and often people who are servers don't have very easy lives. I don't make a lot of money but I still tip ~20% if the service is good.