There's an argument that if you're in a place that's selling $300 bottles of wine, and ordering $300 bottles of wine, there's an increased expectation on the server to be knowledgable about that wine, what to pair it with, etc. Whereas I wouldn't expect much knowledge from a place that sells a $30 bottle of wine outside of varietal and whether it's good or popular.

I still think tipping is BS, but higher end restaurants will attract higher skilled front of house, and so it makes sense that they'll be paid more despite doing the same thing.