Why do Splogs exist?

Tim Bray wants to know what the point of splogs is:

I suspect most people never see spamblogs, but let me tell you, there are a lot of them out there and they get weirder and weirder and weirder. I’m actually baffled as to why they exist.

Oh, this is a simple one. Set up a search feed in your favorite aggregator, and then watch what comes back - especially from PubSub and Feedster, which are just filled with those right now.