Any efficiencies you are seeing will be refactored and stretched out as any business cannot afford to carry fat if they want maximum profit and competitive edge (price).
This whole inconvenience of a friend going to the bathroom is an incredibly weak argument for foregoing the tradition and ceremony of interacting with a person who will provide you with a meal. If you want to live in a McWorld where every step of your dining experience is as sterile, efficient, and touch free as possible then I am sad for you. That's not what a meal with friends and family means to me, it's not just about eating for sustenance.
Why do you draw the line at taking payment?
The reason they get tips is because they are waitstaff, it has zero to do with how hard they work, it's simply custom to tip waitstaff, even lazy waitstaff.
Most employees work just as hard without getting tips (like the people who are actually cooking the food).
This is changing since now people are refusing to work those jobs. And yes, the entire industry is dumb and corrupt for having this practice in the first place, but it is what it is.
Perhaps you are unaware, but:
(1) US federal tipped minimum cash wage is $2.13, not $2.83, but also
(2) Most US states and territories have a tipped minimum wage above the federal tipped minimum (and also, though by a smaller margin, most have a tipped minimum above $2.83, which is PA’s tipped minimum.)
This does not change my point in the slightest, which is that wait staff need tips to survive because the tipped minimum wage is unlivable basically everywhere.
Its the same as the general minimum in several places, and at or above the federal general (not just tipped) minimum even more, so if its unlivable “basically everywhere” that's more than just a tipped minimum problem.