Why Privitize Social Security?

I don't understand the ads that say "He voted to privatize Social Security". The part that gets me is that people automatically assume this is a horrible thing and that it's the end of the world.

When we look at our social security system, as it stands today, it's a failed system. It will not work, and I know that as a person who contributes biweekly into the system, it's 1000s of dollars a year that I will not ever see again. When it's time for me to retire, the current system will not sustain the system to be around for me.

Our government created the system and ran the system into the ground as it is, and it sucks. Why is government control of the system assumed to be infinitely better than giving it to the private sector?

Further to the point why is it that I even have to rely on the government for my retirement?