Using your cited vend-o-matic "restaurant", I would hazard a guess that the card swipe / authorization process is simply sale and does not offer a tipping option. Encouraging folks to "tip" a vending machine would likely not be viewed favorably by the buying public.
Taking the automated restaurant further, to where robots are taking your order tableside, then bringing drinks and food, returning for desert orders, etc, you may see a service charge or tipping option which would be intended to be shared amongst the humans working in the kitchen (same as waiters sharing tips with cooks, host and bussers in better restaurants).
But once the entire kitchen is automated, any attempts at trolling for tips would simply be management trying to up their profits.
In the US, tipping is usual (and expected) in so called full service restaurants; meaning you sit down directly and order at a table with the server.
No tips are usual (but of course allowed and liked) in half-service restaurants, those are restaurants where you order yourself at a central desk, sit down, and your food is brought to your table by the server.
And in self service restaurants, no tipping is usual either (and probably you would get a strange look).