Because an increase on business taxes will devastate the stock market, and the boomers didn't build normal retirements like responsible adults, they have everything in the market and are relying on it to go up forever. And everyone in Congress makes their millions in the markets, and all the biggest lobbyists are directly tied to the markets, and now the pension funds are all over invested in the market and (even worse) private equity, and... you get the idea.
We've decided that "the market" = "the economy" when that's not remotely true, and because of it we now make devastating fiscal decisions (and monetary decisions soon) that are excused because, hey the S&P is at an all time high so it must be pretty good, right?
We will cut spending and entitlements only when we have no choice, and not a moment sooner. Most likely it will be while tens of thousands of our kids are dying overseas fighting the Chinese, or Russians, or who the hell knows who it will be. When mothers see a car with a white top drive by, and breathe a guilty sigh of relief when it stops at their neighbor's house instead of their own, or when the local radio stations list the names of the newest forever heroes as we drive to work, then suddenly there will be a renewed desire to funnel our tax dollars away from able-bodied deadbeats and wannabe-immortal senior citizens...