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 "tradition" is to sit, wait for a waiter to appear. Ask for purpose (lunch? big meal? just a drink?). Then you wait again for the correct menu to appear. Then you get asked for a drink. And wait for the drink. And then comes the longer wait where the waiter tries to detect when you are ready to order, if they see it at all.
Combined, that's some 20-30 mins in and the prepping of your meal hasn't even started yet.
Now if you're the kind of person that's going to be in there 3-4 hours anyway, the ritual doesn't harm, but it doesn't add much value either. It's needlessly slow and inefficient.
Your future dystopian nightmare is already here, and it's fine. In the Netherlands, some sushi restaurants work as follow. You are seated. There's an iPad for everyone, and people just tap what they want. Some minutes later, your food arrives. This supposed cold-hearted efficiency means I get to spend more time engaging with my friends, the very point of the visit.
By the way, you're not doing restaurants any favors with a slow and long visit. It means they can't use your table twice. So finish your meal in 1.5-2 hours and if still not bored with your friends, go to a damn bar.
This ritual or ceremony of waiter, menu, waiting, ordering, signalling for the cheque that you apparently find vile... I enjoy it. Any inefficiency you have declared is part of the experience of going out to eat.
You want fast food? Go get fast food.
You want a butler and cook? Hire them.
You want to go out to dinner? Here's a waitress, menu, and some time for walking back and forth between their station and your table and their other tables in their zone.
All of this is, or at least should be, factored in to the restaurant's business. It's been 100 years, at least in the US. If they don't get it by now, at least you should.
A restaurant wants to know your order. Why does this simple thing take 20-30 mins? Whom benefits? How does it enrich your experience exactly, this useless waiting and pointing at a menu?