Yes, your logic is pretty much spot on. Meetings that people are welcome at generally attract little sweeteners to make the meeting or conference more bearable - whether it's sandwiches, cakes, teas, coffees, or biscuits.

Generally, if you walk in to a room and nobody offers you a tea, coffee, or a biscuit - there's a reasonable chance that you're going to get your arse kicked for something.

If you don't mind me asking - have you not heard the phrase before because it's an expression you've not come across before, or is English a second language and it's meaning is implied rather than explicit? To me, your logical approach suggests the latter, and I'm asking out of sheer interest :)