Saw someone on Reddit who said that their mother would keep leftover food sitting out on the counter, un-refrigerated. She couldn't understand why it was growing mold several days later. In her mind, "cooked" meant "safe from spoilage".
Jokes aside, I think it's simply because grapes are so sweet and naturally high in sugar. And then you add more sugar for jelly-making; it's a bit gilding the lily, I guess. Grape preserves seem to be uniquely American, like cheese in an aerosol can.
https://www.fodors.com/community/europe/no-grape-jam-in-france-961126/
5,000 years ago, Ancient Egyptians would treat infected wounds by applying a poultice of moldy bread. Nobody knew why, until 1927, when Alexander Fleming made the association between moldy bread and Penicillium, the type of mold from which modern penicillin is derived.
Hey, Bertie!
Hey, Terry!
Hey, Gary.
Hey, Drew! You know we'd never let that happen.
*siiiigh* Well, Spring may be here, but there's still a bit of chill in the air. Today's weather is 38 F/3.3 C with light rain. Fortunately, the basement area is big enough to host a moderate gathering, with enough space for the kids to play some games indoors.