Scenario as I imagine it: OP and elderly parents are out for walk, stroll past cafe. Conversation along lines of "Shall we pop in for a snack and a sit-down? Well, I'm not really hungry dear, but perhaps we'll just have a little something." They go in, events of opening post ensue.
Question: Has the cafe owner gained the sale of at least the cream tea from punters who might otherwise have not entered his shop? Or has he lost the use of a precious table to 3 tightwads when he might have enjoyed the patronage of a MN poster ordering 17 full roast dinners?
I've never run a cafe, so I'm not sure which is better - basically "a bird in the hand vs 2 in the bush"?
Also, IME those pots of tea "for one" are huge and contain way more tea than I would normally drink. If I were to drink the entire thing by myself, I'd probably be going to the loo several times, thereby using vital pence of loo roll and hand wash.
Perhaps the answer is to purchase said menu item, then not consume it and in fact, go home. Then the cafe owner gets the money and his table remains free for the next customer. 
Disclaimer: We generally always order a thing per person in cafes, especially where scones or cakes are concerned. Because yum.