Why, just why did they think that a curved top was more important than the ability to stack more devices together, or to make it easier to fit in a simple and precise slot.
It's a common feature added to many objects. My laptop, furniture, shampoo bottle, my backpack, my smart phone etc.. etc.
Whenever I see an aerodynamic building I just laugh, because when I throw my ugly smart phone into the trash, at least the aerodynamics makes it a bit faster while it's flying through the air. But buildings? Why? those things don't even move.
(OK, you were probably being sarcastic! But wind engineering is cool!)
They are trying not to slow down the wind, so wind turbines will work well.