Can't put certain decor on picnic tables- Why?!

Originally posted by LohBoi

It's because picnic tables occupy a 4 wide space but only have a 2 wide flat area, and they didn't want to let you place things "floating".

However there's a trick with Teleporters, where placing one on top of each other, then placing a piece of furniture, then breaking the bottom Teleporter leaves the piece of furniture floating and you can place nearly anything under it