When the Sims 4 introduce curved decks to the game, I jumped on them to provide curves to my blocky homes. I created an entire series of homes using this feature on a hybrid of Art Deco and Mid-Centu...
I think it's probably because there'd be a lot of placement issues, a door wouldn't work on a rounded wall, a window wouldn't either, you couldn't place any other items on the wall as it wouldn't work, etc etc