"Why make everyone try to contribute?"
Because its is a human need.
To feel like they are contributing to the family / tribe.
You also need everyone to feel like their work is balanced, else resentment starts.
However, that said, many people will do little more than getting rid of weeds on the daily.
During harvest season, it is, of course, all hands on deck.
You're not getting My point. Yes, We will contribute, but in ways We LOVE to do. Not schlepping into the bank to sit at a teller window for 8 hours 5 days a week. Or tilling ground when plenty of Others are doing so. Or harvesting, even. Why would We need "all hands on deck" when 80% of Us are not needed NOW for that and We are already automating such work as We type? When money is removed as a motive, We will do things for the social currencies.
Social Currency (article): https://peakd.com/informationwar/@amaterasusolar/social-currency