That's a very good question. I've debated dropping Snow Leopard support in future versions several times. As you likely know, it can be difficult to develop new features and support new OS releases while maintaining backward compatibility with old OS releases. In development of the next release of Pear Note for Mac, I actually did drop Snow Leopard support (and Lion as well) a few weeks ago. But then I found a way to work around the problem I was having without losing 10.6 compatibility, so I added support for 10.6/10.7 back in.
So, I have not dropped support for Snow Leopard yet, and there's a good chance I won't drop it in the next update. But it won't be too much longer before I do drop support for it. There just aren't very many users using it any more, and the maintenance burden of it continues to grow.
One note to anyone else reading this - this doesn't mean the current version will stop working on Snow Leopard. It just means new versions won't work on it. You can keep using the current version on Snow Leopard for as long as you like.