To me, it's fairly obvious that it can be stressful having to choose between a number of options in cases where the social expectations are unclear. It's partly for this same reason other situations can be stressful, like first dates, job interviews, encounters with police, discussing bad news, etc.

Now, I don't think that's sufficient to say that all tipping is to be avoided, but I certainly understand the urge to avoid it, ceteris parabus.