Let's start with the obvious. The less money put into the government plan, SS, the less money the government will have available to pay out.
Some people did invest privately and ended up with nothing. Folks like the Enron employees. Many others took a hit with their stocks when the bubble burst.
It's fine to say a few years later things improved but what would have happened to those who retired at that time? For example, let's say someone had $100,000 in stock and it dropped 25%. They're left with $75,000. Now they need $25,000 a year to live on so over the next two years they take a total of $50,000 leaving $25,000 invested. Then the market picks up.
As you mentioned from 2005 till now the money would be up 5.5%. That's great for the person who didn't need to touch their $100,000. (First it dropped to $75,000 , then increased to $105,500.) What about the person who withdrew $50,000, over two years, to live on? How much do they have left? The stocks that were supposed to regain their value have been cashed out.
Dozens of countries have produced health care plans that save money, savings on average of 30% + compared to the US. Are Republicans prepared to implement a full government health care plan?
What don't people understand? Dozens of countries have taken a medicare plan and a medicaid plan and general health insurance plan and rolled it all in one and are saving over 30%. It's been done. There are dozens of examples and not one plan has been scrapped. Not one country has reverted to a "pay or suffer" system.
There is no shortage of examples but until the decision is made to have one government plan it's going to be constant bickering. On the up-side as different initiatives of the ObamaCare plan come on line people will realize the benefits. One more Obama Presidency and a lot of this nonsense will be history. One medical plan for everyone.