Is the problem you are solving really a problem?

From "You and Your Research" by Richard Hamming :

http://www.dgp.toronto.edu/~anab/grad/hamming.html

    I started asking, "What are the important problems
    of your field?"  And after a week or so,  "What
    important problems are you working on?" And after
    some more time I came in one day and said, "If what
    you are doing is not important, and if you don't
    think it is going to lead to something important,
    why are you at Bell Labs working on it?"

    I wasn't welcomed after that.

It doesn't necessarily apply, because that was research he was talking about, not "making money" or even"making a living."

Even so ...