If you make 20$ and hour at your job, pretty sure if your manager came up to you and said "even though you worked adequately this week, the company is a little short on cash so we are going going to pay to 10$ an hour for the week" you'd be upset.
View tips however you want, but this is exactly what is happening when people don't tip well because they "can't afford to". There are other establishments to eat at that do not require a tip. If you can't afford to tip decently (for servers who deserve said tip) then maybe you should wait another day or two, or however long it takes for you to save up 3$ more dollars to add to that spare 2$ you have in your pocket before going out.
Call it entitlement or whatever you want, but tips are 95% of a servers income. We do not make pay checks. You're no more entitled to good service than we are to good tips, it should be a mutual relationship. If tipping standards weren't the way they were, you'd be paying that extra 3$ in food costs anyhow. Food is able to be put at a much cheaper price because restaurants don't have to pay their wait staff a fair wage.
No server should be entitled to their tip, they should feel they need to earn it. Perfectly true. I'm not defending bad service here, nor am I against tipping less for poor service. That's not the discussion.
If you go to a Chili's and get a 50$ check, and you tip 2$. I make 0$ off of you. Yes, you're a bad person if you are doing this. The entirety of that 2$ you gave me is going to the restaurant as 4% of sales is a pretty standard tip out. If you give me 0$ on a 50$ check I'm LOSING 2$ out of my pocket because I still have to tip out based on my sales.
I don't like the servers who feel they are entitled to get good tips, and it's hard to make arguments about tipping as a server without coming off like one. So that's not my goal here. A server should meet all of a guests needs with a smile regardless of the situation, regardless of tip. However, a patron should tip properly when servers do so.