There are different minimum wages for people in e.g. restaurant service, which is to me the quintessential tipping experience. If that went away, it could perhaps pave the path to less tipping overall

But I'm not defending the argument, just adding to the debate. I'm fine with tipping, personally, because I think it aligns incentives to encourage good service. That good looking people get better tips doesn't bother me in the slightest—life isn't fair.