It just seems so unlikely that 18 women would be of one accord in terms of ability (time, resources, skill) and inclination to participate in this rota.
I would find it easier to understand how it came about if there were 4-8 maybe. That's small enough to be a friendship group, to have a history, to have maybe all sat at the same table during a works do and come up with the scheme, or to all live close together and meet socially.
But 18? That's a really big group, likely to be diverse, unlikely to meet regularly in person. Maybe it started small and others joined in, which brings up the question of pressure and feeling of obligation.
Like many on this thread, I also remember my mum sweating over the bloody cricket tea in the 70s & 80s, like her MIL before her. She didn't enjoy it, but it was expected and she would no more have expected my dad to do it (or even help out) than she'd have expected him to fly to the moon. She also wouldn't have considered telling them to do a running jump and sort it amongst themselves.
Fast forward 20 years, and my DB plays cricket, makes "tea for two" if it's a home match (half a loaf of sandwiches, crisps and a packet of kitkats or similar - he's not much of a baker), and it would never occur to him or my SIL who is an amazing cook, enjoys baking, but has 3 small children, a demanding job, and a busy social life of her own, to delegate this job to his wife. My mum thinks this is marvelous.
And lo! The men set the table, make the tea, and wash up without involving their significant others as well. Who knew, all those late 70s Saturdays I spent at the cricket hanging about the boundary line with DB and getting shouted at if I ran in front of the screen, that a woman's presence in the kitchen wasn't an essential part of the game? 