Ok, here are my reasons:

1) I would like to be able to talk about politics with rational people
2) Understanding more of how the world works could be useful in other areas.
3) I want to be able to make references to things that might be construed as political without having the entire post downvoted to -6 because I'm not allowed to talk about politics.
4) I am increasingly worried about the radicalisation (Assuming it really is increasing) of Less Wrong and I think the problem is that crazy views get too much credence here, due to an unwillingness to criticize by more rational people. (Biggest issue for me)

Edit: I don't get why I receive so many downvotes in a matter of minutes for answering a question as honestly and helpfully as I can manage. I see the same in some of my other posts. I somewhat suspect this is entirely based on party politics, where I am perceived to be criticizing party X in the original post, and so have unrelated posts downvoted by angry people. But maybe I'm missing something.