There are times when you need perfect right angles to make the building better. Other times you don’t.
One such instance is in the case of building interior walls. If you want the rooms to sound better, the walls should be slightly not-parallel. The sound will bounce around in a more pleasing way.
In our work, we get to choose where to add in (or keep!) an element that might be unexpected and appear incorrect. But it might make it even better.