For every place that doesn't allow 16-20 year olds, there's probably a hundred or so places that will. Give them your business. I'm 43, and it's nice to go to a place where there's an adult clientle that doesn't involve lap dances.
Also, it seems like any place I go for dinner that's more on the expensive side, there's a higher & higher chance there's going to be a baby or toddler crying their eyes out, ruining my meal., But I digress.