$5 on a $100 bill? In the US? That's awful.
I can understand the logic though of a fixed tip. There are all kinds of situations where a server spends the same amount of time/effort for each table and get different tips based on what the person ate?
Why does that make sense that I would tip more because I got a steak instead of a burger and the server had to just bring it to me in either case?
I guess I tend to eat at the same 3 restaurants around my house. They all know me and are also my neighbors. The social pressure to not be "that guy" has pushed me to tip generously I guess.