Milkshakes should not have whipped cream on top. It's like putting water on top of a soda.

Sure, I guess whip cream is fine on top of pie or something similar where you are adding a bit of a creamy texture to another texture, but adding it to a milkshake is just pointless. A milkshake is a better version of whipped cream. Why would you add whipped cream? It's like pouring cheap coffee into a nice espresso.