They get into power and dismantle projects, don't provide enough funds, etc and then point to how bad the project is and say a private profit driven company should do it instead.
Regarding profit-driven companies, I worked for GE's Space Division on a big NASA contract back in the early-to-mid-1980s (and it was a great experience). Unfortunately, the defense side of the division was caught cooking the accounting books and the entire division, defense and civil, was barred from bidding on new government projects. Temporarily, of course, but long enough to result in our facility being dissolved after finishing a couple of smaller commercial projects already in the pipeline. (Coincidentally, one of my friends at GE had a master's in astrophysics and had spent a summer or two at Arecibo.)
At about the same time, Rockwell (I believe was the company) was caught charging defense project cost-overruns to its Shuttle contracts. On the plus side, private-sector personnel don't have that "lazy" gene that public-sector personnel have, so, aside from the cheating left and right, we're better off channeling money to the private sector, who are well-known for the superior quality of their goods and services.