Two reasons:
1) Pride
2) He wants the people to suffer so he can blame the suffering on Republicans.
Your politics have made you a wee bit cynical. That's not good for the spirit.
Nothing cynical about it. That's exactly what he is doing. Watch and listen to what he says. He is happy that the shut down happened because it gives him a weapon to attack the Republicans with. He has absolutely no problem that people are suffering so long as he thinks it benefits him politically.
Look at least half the left leaning members of this board. They are acting the same exact way. They are celebrating that people are suffering just so they can attack the GOP.
As much as i don't agree with Democrat policies, the last thing I would ever consider doing is to take pleasure in people suffering because of them. Quite the opposite. I don't like that people are suffering which is precisely why I oppose those policies.
What's going on in our government may be political games by the politicians and some of the people. But reality is it's effecting the lives of people. Many will suffer. Some will even die because of bad government policy. Some people might not think that matters as long as a D or an R has power. But I don't. We need to clean corruption out of our society. And the best place to start is with ourselves.