As a kid, I remember the seat on the aisle being empty during much of the day at assemblies. My dad was helping with actual cooking, prepping food, serving food and coffee to the 'bigwigs' during the session & cleaning pots and pans the rest of the time. I remember volunteering to work at the sandwich assembly line tables - morning and afternoon. I'm sure the WT wanted to end that business because too many were missing out on the sessions.
I've always wondered if the change occured in the United States (it was common to bring your lunch in England and Japan in the 80's) because the loyalty of some brothers who were in the supply chain business for assemblies might have come into question - when Peter Gregerson disassociated himself. He was very active in the southeast US and had a chain of food stores and access to food wholesalers.
This is pure speculation on my part based on 'gossip' I heard years ago. Please correct me if I'm way off on this one!