Chris adds, if I may be so bold as to restate his comment without quoting, that in some careers there can be a huge difference in pay (and, I assume, working conditions) based one whether (or what kind of) degree you have. Knowing how to do something, in other words, is all well and good, but some employers also want an official looking (and very expensive) piece of paper from you as well.

The moral of the story: follow your dreams, but never forget that the rest of the world might be following a slightly different dream.

I know that in my current job, I make more than most of my colleagues because I have an MA. One of my colleagues makes more than me because he has a Ph.D. Another gets the Ph.D. pay because he has a J.D. That's the way of things. No one cares much whether we are all capable of the same level of performance.