Actually I think because it's none of our business. No matter what they pay, it's still a hell of a lot more than what your average American pays.
No, Buffett isn't doing anything for me, it just happens to work out that way. The reason we have lower capital gains taxes IS to encourage investments that do benefit all of us.
And that's the other thing that bothers me so much about these topics. The wealthy do benefit our society greatly. They create jobs, new taxation, products, services, and all the left can think of doing is cutting them down. The people they defend are the leaches of our society that contribute little or nothing, create problems for society, and people we can generally do without if you ask me.
I'm sorry, but I just don't understand that mindset.