It's up to you whether you think you need it.

I'm a person who tends to accidentally throw my phone around a lot, and don't use a case (cause the added bulk makes me throw it around even more). Often on ceramic tiles, often with added velocity from me walking or hitting it in the air while trying to catch it.

My iPhone 13 Pro still survived 3 years, and only had some scratches and bruises on its corners, but nothing broke (still in use, by someone else now). My iPhone 16 Pro after a year of that same treatment is almost unblemished (a small bruise on one of the corners).

These are, in practice, extremely resistant to damage.