Do you really know why ? Take Social Security, the government really needed money and a new open tax was not an option, result was Social Security. It was designed as a money machine, hows that you ask, simple, when it was started the retirement age was 65, the main difference was the actuarial tables listed the high average age as 55 for surviving, most who paid in to it never survived to collect a dime, that proved true in the case of my great grandfather, grandfather and father, none ever collected a dime. The money was also put in to the general fund, with congress 'funding' any outgoing payments with every budget, they got to play pig farmers with the rest for whatever pork projects they wanted.
Same with the medicare programs, it's funded and paid for with MY tax dollars, only problem is CONGRESS gets to do the funding every year and gets to play pig farmer with the rest. If every dime social security paid in every year was put in an untouchable fund drawing 4% interest it would be self sustaining now, actually about 20 years ago.
Our elected officials have been screwing this country since Kennedy was president, every single administration has screwed it more every time. None of these clowns has the basic understanding that when you are digging yourself in to a hole the first thing you need to do STOP DIGGING, buying more shovels is not the answer.