Not sure how different things are between Germany and the USA, my experience regarding catering is that clients who understand we're stuck in the ballroom or tucked in under a staircase for hours on end, often waiting for other people to make up their mind about something trivial (or spend an hour revising their powerpoint during their 20 minute rehearsal slot). They know that in spite of the apparent civility of everything, there is some "suck" involved and that good food and beverage hospitality is appreciated. The other clients either don't know, don't care, or don't have sufficient budget. They have grumpy crews.
Overheard from a medical client's meeting planner: "...and the afternoon session is Coma Inducing, I've ordered espresso service for the AV technicians." That could be interpreted a couple of ways; probably a good thing lobotomies are out of fashion.
The gigs I've learned the most from have been industrial safety conferences and aerospace product introductions. Met and worked with some awesome folks, both presenters and technicians.
I keep saying this: it's a great time to be in audio.