As a user of the site, what is preventing you from chipping in for your usage?
I upload content, and used to listen to it, but now I don't. Some others have downloaded the content, but it wasn't critical. I don't use the site enough on my own to justify donation. I think it is a great service- really! But, I would bet many feel the same way. Unless it is really helping others that you care about, why donate? It has never significantly helped me personally, or any that I know. I would rather donate to a charity that helps those in need. But I'm glad others donate. It is preserving history. It is just a matter of priority.