My understanding of the tea trolley is that somethings just are worth doing, full stop, and rather than say 'you can't have this' it was 'let's be sensible and have one person do the fiddling and everyone else will stay on task until they have their cuppa and nibbles.' It was Modern! Efficient! Hygenic! (sorry, I think some ad copy escaped.) And the re-fuelled could get back on task and not be grumbling about no tea for them.

Of course part of the reasoning for the free food at certain types of employers is they have their campus off in nowhere so there isn't somewhere to run out to. You wouldn't want to see the code that would happen after two days of not going home and left to their own devices. Bagels mold without refrigeration pretty quick.