How I see it this is a problem for the providers of the cafe service to solve, not the customers.
But we don't even have to guess. Big businesses that are very careful about monitoring things like this, such as Starbucks, actively encourage laptops (with tons of power, wifi, rows of single-person desk tables) so maybe your intuition about what is profitable is just wrong? I mean you've thought about it for ten minutes and were already coming into the situation annoyed because you want to sit down and someone else was there, and Starbucks are running this business full time with I would guess people dedicated to thinking about this kind of thing.
I'm more inclined to believe their reasoning on it.
Sorry, did I say something to offend you?