I have seen a similar pattern where learning new ancillary skills have increased the quality of my core competency.<p>I think side-projects are a decent proxy for curiosity and industriousness, which I try very hard to evaluate when interviewing candidates.  However, my line of questioning for this has to do with what complaints people have with their tools and what they have done to overcome them -- this shows a similar desire to have internally-motivated programming tasks and a desire for understanding more than simple project requirements.