People tend to think it's a lot more of the federal budget than it is:
"For example, in 1997 the average estimate of NASA's share of the federal budget by those polled was 20 percent."
From
http://bit.ly/aAg7I3
Er, try 0.58%. But this misconception is a real problem: if people think there's just
tons of money in there, cuts don't seem like a big deal; in fact, they seem entirely reasonable.
Add to that the unwillingness of our political class (both parties) to do anything about spending and cost growth on defense, medicare, and medicaid and you've severely limited "what you can cut" to NASA and a handful of other programs, even though cuts to those are a fractional percent of the budget and barely enough to even register over a 10-year window.
Leadership takes hard decisions. Our "leaders" have shown no interest in same.