Round, traditionally the dough was spun to make it super thin Square, simplest shape of getting the round pizza boxed Triangle, when you split round edible things you end up with a triangle, also is more stable to eat

Understand women? Then you can breathe in space too. Just say yes. ^^

Or if you order from Jets it is a rectangle pizza in rectangle box cut into rectangle slices. You are ordering from the wrong pizza shop. 🫡