Why does superman have to change from his clark kent clothes into his superman costume before he flies?

He looks like a fruit in those leotards and cape.Why does superman have to change from his clark kent clothes into his superman costume before he flies?he doesn't have to, he just chooses to in order to keep his identity a secret. If he wanted to, he could fly while naked or while wearing his kent clothes.Why does superman have to change from his clark kent clothes into his superman costume before he flies?so no one knows who he isWhy does superman have to change from his clark kent clothes into his superman costume before he flies?like wise why do people change into their pyjamas going to bed, they could still sleep in their working clothes.

it's just a fantasy film, but perhaps it does make him more aerodynamic.Why does superman have to change from his clark kent clothes into his superman costume before he flies?
Superman does'nt like flap his arms as if they were wings, or anything like that to fly, the only way he could fly is by passing wind with superhuman strength. There is a strategically placed hole in the seat of his superpants through which the expanding hot gasses pass through. You cant see it because the cape hides it. You may not like the superman costume, but, you must admit its better than flying through the air with a big hole in the seat of your trousers.