Does your cell phone need a case? No.
Is your cell phone easy to damage? Probably
Will a case protect your phone from damage? Yes, some damage but not all damage. The glass can break if it’s hit with something hard.
A case makes it harder to put your phone in your pocket and harder to take it out of your pocket. My iPhone is four years old and doesn’t have a case. The case made it harder to use.
Besides, your phone is expensive. take care of it. Don’t drop it. Make sure youu don’t drop it. then you don’t need a case for it.