Because too many Americans want their government doing everything for them, and it nearly does. But we only get a few votes each year. This gives the politicians the opportunity to do a lot of things wrong so long as they do more things right than their opposition likely would.
Let me put it this way. I can about the national debt, generally following the Constitution, specifically allowing freedom of religion, illegal immigration, lowering spending, global warming, racism, NASA, good treatment of America's allies, treatment of America's enemies, free trade.
Every year I get just over one chance to choose Democrat or Republican on all these issues. I don't get to say "I'll have a Republican on following the Constitution, a Democrat on global warming, a Republican on illegal immigration, a Democrat on NASA..." Nor can I choose specific models "I'll have a far right republican on freedom of religion and a moderate republican on free trade..." I get to choose 1.1 person a year.
On the other hand in electronics I get to choose an Apple laptop, a Samsung handheld computer, a philips stereo, a Sony TV,... And when I choose that Sony TV I get to choose from so many models. And if I find I don't like one of these items after getting it home I can return it.
We need to have less control by the government and more control by the market because market control generally means freedom and excellent service.