question about the product development process..

Great points:
ONE:
> What is the MARKET for this
> product/idea/service?
TWO:
> But these creative people who had invested a
> lot of their time and money and effort into
> a project just COULDN'T believe that NOT
> everyone would want it. It hurt their
> feelings.
THREE:
> He created a product he LOVED. He just knew
> it would make him rich, and what he found
> out AFTER spending his time and money and
> effort on this product was that NO ONE
> wanted it.
FOUR:
> I also found out how UNREAL people's ideas
> are of doing remote direct marketing or
> product development.

Good points in this post...and now the question:

Why do we pick certain topics? Why do we focus
more on the product rather than the market?
What is causing this confusion? Please stay with this topic and go deeper...

Ok...here is my theory and perhaps you and some
of the other product developers can comment on
why this problem is happening...

Theory: Many books,courses etc exist which state
and imply you can "do what you love" and make
money. I think this idea of "doing what you love"
has been transposed to " creating a product
YOU LOVE"...and the other part of the equation:
After you do WHAT YOU LOVE the money will follow..

Looking for comments and viewpoints on how you
can integrate what you love with the appropriate
market and/or if you should consider market
first before "what you love"...