Wasn't this all to avoid the "tax/profit" issue?
Lunches disappeared about 10 years or so after the "donation arrangement" for literature was put into place.
I think they went away primarily because gluttonous JWs were each scarfing up enough food for a half dozen people, and taking it back to their hotels or home after the DC was over, and not contributing.
"Free food" is as irresistible a call to JWs as "free beer" is to a frat boy.
I think a secondary reason was fear of litigation. You had sandwiches made with questionable lunchmeat sitting out at room temperature, or directly in the sun, for hours at a time. I'm quite surprised there was not more food poisoning cases at the DCs.