As a software engineer, basically all the skills I use to do my job on a day to day basis are things I've learned from experience, or informal mentorship from other engineers, or reading blog posts on programming practices and then applying those things and seeing what works and what doesn't.
But to an economist none of this counts. A 24 year old that just started their first job after getting a masters degree in CS is considered objectively more skilled than someone with an undergrad degree and 10 years of experience.