Version Control Software makes life a lot easier for you as an individual developer. It is a great form of undo or figuring out what caused things to break or slow down.

For working with other people it lowers the barrier to entry for making a change. They can browse the source code. It makes merging code a whole lot easier because of the history involved.

There are a lot more reasons than those but to sum it up, just do it. It makes it difficult to work with you such that the source code being available is only good for forking. I and I would assume some other developers would skip over providing any assistance without it. There are many articles all over the internet that you can find (Joel on Software might be the most famous high level one) about revision control being one of the most fundamental tools of software development.

Oh and the garage provides web hosting. People don't want to have to read every talk post to know what the status of you package is, where the download page is, where the package testing page is, where the thread is, where the source code is, any help you might provide, etc. I've since moved all of mine over to the wiki though to (in theory) allow other people to help keep it up to date).