I have never heard of that. My sister and I paid for my dad's cremation, no one ever gave us a penny, though one of my half-sisters sent a wreath for the burial ceremony at the veteran's cemetery. When one of my closest friends died, no one gave anything to his family, other than hugs and condolences, maybe a card, and some people close to the family sent wreaths. When my uncle's mother died, again, no one gave anything. Then again, none of these people had obituaries, and then again, maybe traditional American people tend to do things differently (I am a first generation American, so I wouldn't know).
I, for instance, had never heard of funeral parties where people bring food, laugh, and celebrate, so that concept was bizarre to me, same with celebrations of life, because my family mourns death heavily (though we're also very private people, with few close friends and we don't really do parties, ever). I first experienced a celebration of life a couple of years ago when my ex's nephew died tragically in his mid-20s and they had rented a huge banquet hall in a golf course and catered food, had some of his friends coming up on a stage singing, sharing photos, and jokes. I didn't know what to make of it. I guess we're all just different...I don't see why they had to be so snarky with you for not reading their minds and knowing what you were expected to do at the funeral. Maybe this is something the whole family should have discussed prior to the services, if it was so important to them?