There's an obvious difference between having theoretical knowledge of a subject, and have practical hands on experience. That's why plumbers and electricians have apprentice programs. It's not enough to know that this wire is hot, this one is cold, and this one is ground. You also need to pull the wire through the conduit, connect the screws to the outlets, install the breakers, etc. You don't get that in a book.
Some people have an aptitude for the mechanical side. They like to get their hands dirty doing things. Given a solid educational foundation, I have found that those people tend to be successful. Others use their personality and people skills to get ahead. For many occupations, that's perfect. If you are in the sales field, personality has a bunch to do with your success, as long as you have sufficient knowledge of the product. Adding 10 years of hands of experience on top of a degree is a bit of the best of both worlds.
There's a saying that has a bit of truth... Those who can, do. Those who can't, teach (or they ask if you want fries with your burger).