I wanted subgrid a few years back. Imagine you need to show 3-4 pricing cards next to each other. It can't be a table, the cards have padding, an outline, shadow, etc. Inside they have rows of features. But some of the items aren't just a single line of text, they wrap around, and you need to have the heights of those inner rows align between the cards. It's not possible without a subgrid or some custom JS code.