Tips Jars and "Conscience Money"

In talking about self-publishing and ways to monetize online short fiction, several people mentioned an online Tip Jar, a way for readers and fans to contribute a few bucks and support me as a writer.

It's a nice thought, and I truly appreciate it.  But it's not something I'm going to do.  My reasoning comes down to two things.

1. I don't need the money.  I want to get paid for my fiction, sure.  (The blogging I do for free, for the community and the secondary promotional benefits.)  But...