You're right. There are several occupations which have legal entry requirements. You can't be a doctor without getting a medical degree.

However the number of professions that require a formal degree is very small. (And notably, programming is not one of them.) If you take any large group of random people and asked them, you'd find close to all are not required to have a formal certification.

Generally yes, people with (any) degree are more hirable to (any) job. The skills getting a degree are generally useful, and make a candidate more employable. But if you already have one, you already have that.