Y'know, I've ordered pizzas for quite a few events (sometimes a large number of pizzas), and I've never once had a pizzeria ask about the nature of the event. It's always been something along the lines of:
"I'll take [X] number of pizzas, delivered at [location/time]"
"OK, that'll be [cost]" "Thanks"
I’m talking about events that use their facility.
For most stuff you are exactly right. And even if you say your event is for such-and-such, they would probably supply the stuff if they are dropping off food and getting paid.
And I’m betting that most people calling in such an order don’t make a point of telling the pizzeria what the nature of the event is, either.