Yeah I exercised with only my body weight for many years. I was pretty fit. Now I started going to the gym and one thing I discovered was that i never exercised certain muscles before. I had wide arms but small shoulders. This is because at home, you usually dont have all the equipment to exercise all parts of the body.

This may be fine though. For me it was fine for many years. But now I wanted a larger uppger body and that means shoulders and back and biceps.