Honest answer is because the registered voters of America don't really seem to care! Only 57% of registered voters voted in the last presidential election in 2012. Fox News Channel keeps bringing out corruption with contractors, etc, and some Senators and some Congressmen talk about it, but never do anything about it. Why? Because they know that the voters aren't going to vote them out of office! Over half of voters don't even watch the National News and don't know what's going on.
Politicians have for too long traded entitlements for votes, and once established become entrenched. Once a jobless nations tax base dwindles to a trickle and has to borrow to write checks to couch potatoes it becomes a matter of time until that system collapses.