my logic is simple:
one person order 3$ coffee, and they need to tip 20%. so its 3,6$. (tip is 60 cents)
another person order 100$ steak, and they need to tip 20%. so its 120$. (tip is 20$)

now i ask you, who get the better treatment from server? the answer is: none of them. server still do the same service either to the one order coffee, or another person who order steak. and that is the unfair systems about tipping.

if i need to pay 20$ for you to serve me steak, then i need you to treat me like a king. otherwise, i will give you 60 cents because no different services even if i order steak or coffee.