I think it's fine to only tip 15% in a state with no server's wage
are servers paid well in your state?
Yes, so I sympathize with all kind of workers, except waiters.
As a customer it's your right to leave as much for a tip as you want. You're not forced to tip certain amount.
It's easy to just give 15% then isn't it?
I think you're justified in leaving 15% in those states, especially since it's above the minimum of 0. I'm sure most of the servers are pleased to receive your tip.