Here is why this statement is true. If the public deems something worthwhile at a given cost and it can be done at that cost plus a reasonable profit, the private sector will move in and do it for profit. All other things the govt. will try to do, will be done at a price higher than the public deems worthwhile. The best way to create jobs is for govt. to reduce the cost of doing business and that is with fewer regulations and lower taxes. When the govt. does this, more things will be done and that is when the economy gets moving.
There are some projects that are simply too large in scope for the private sector to finance on its own. Hoover Dam is one such example, the Interstate Highway system is another. Such "privatization" extremism also begins to violate individual freedoms in other respects. For instance, private ownership of our transportation infrastructure establishes natual, local monopolies and violates individual's rights to move about freely.