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?
There is a ton of abuse in the food service industry in America, not the least of which is paying servers less than 3 bucks per hour, and thats one of the cushier jobs. I was a server a long time, and sometimes you make the money in tips, sometimes you don't. I knew a lot of servers who put up with workplace abuse because of the illusion of easy cash the job creates. BOH staff work harder and usually take home even less.
Ordering from an app is great. No mistakes, no forgotten orders, and nobody abusing the machine.