But I wonder, have you observed that there are some people who naturally tend to be more interested in getting involved actively in personal development efforts of the kind you support?

Yes and no. What I've observed is that most everybody wants something out of life, and if they're not getting it, then sooner or later their path leads to them trying to develop themselves, or causing themselves to accidentally get some personal development as a side effect of whatever their real goal is.

The people who set out for personal development for its own sake -- whether because they think being better is awesome or because they hate who they currently are -- are indeed a minority.

A not-insignificant-subset of my clientele are entrepreneurs and creative types who come to me because they're putting off starting their business, writing their book, or doing some other important-to-them project. And a significant number of them cease to be my customers the moment they've got the immediate problem taken care of.

So, it's not that people aren't generally motivated to improve themselves, so much as they're not motivated to make general improvements; they are after specific improvements that are often highly context-specific.