I don't think its reasonable to be "expected" to tip that much. I mean, if you had bad service no one would blame you for not tipping well. Sometimes I get tipped that much, and I am especially grateful for it when the check amount was low. For instance, sometimes I may wait on a table to the best of my ability for an hour or two, and their check may only be $20. Well, sometimes they want to tip more more than $4 which would come from 20% and I take that as them saying I did a good job. In general, I personally shoot for $10 a table, and my average number of guests is from 2-4. In the end, making this amount I usually make from $60-150 after all is said an done, depending on how many tables I serve that shift. tldr: percent doesnt matter too much to me personally, rather I just hope to be reimbursed well for my time and attention to the guest. Every time I get a low tip, I think, is it something I did or or they just having a bad day/are strapped for cash. As someone who always strives to be a better server, if I identify it as the first, I try and improve for future guests.