There does come a point where enough is enough, and then there is the fact that it does take more effort to sell something even though it may be a small effort. I still need to come up with a way to collect money for example.

I think the reason I post free apps that are closed source is simply because I love full featured freeware myself, so I like sending it out to the world with the same idea in mind. When I can get a significant task done with a completely free software package it feels great, so I like to share that.

Really if the answer of 'why not make it free?' comes down to 'because you can get piles of money' then it all is about what your motivation for releasing some software is. Not everyone is motivated by more and more cash.