A 4 year degree will make a person academically robust, and "analytically mature". Both these things are critical in a career where lives can be lost because of your actions. A degree is also a great and quick method to check if a person has these attributes, or at least has the propensity to have these attributes. Can you still obtain these attributes via a long work history and experience? Yes.

Passion for what you love doing is most important, and passion is perhaps the best teacher. When you are both a fan and practitioner of your craft, it is easy to become a master of this craft. Often, a person becomes an expert.

One of the things about college (I started college later in life, but worked in my industry for about 12 years), is that I learned things like communications (written/verbal), how to properly research and present ideas, for example; organizational management, systems engineering and analysis, and things like discrete math, which I still use for systems logic. These are things I would have never learned by simply loving my craft, learning all that I could learn about it, and only it.

There is value in a 4-year degree, although passion and long work experience can and should develop similar attributes in a person. My preference is that pilots get a 4 year degree and significant experience behind the stick.