Especially since the support they have been given is, well, inadequate, is the best word I can think of. Now, you might think that $2.5 billion is plenty of funding for anything, but keep in mind that 1) this mission is the very cutting edge of aerospace engineering and technology, and as I have explained a few times before, the development of new science and technology is the most important economic activity any society can undertake.
2) We face a massive cultural problem in the United States and the developed world, with every generation since the end of World War Two steeped in a pecuniary culture that is increasingly useless, destructive, and predatory. This pecuniary culture, as Veblen explained, promotes and rewards socially destructive economic behavior, such as usury, at the direct expense of economic behavior that actually creates wealth and builds a better future for society. NASA has been one of the precious few institutions in our society that encourages kids to think positively about science and technology.
3) $2.5 billion is a mere fraction of a second of trading in the completely useless torrent of financial trading of stocks, bonds, options, futures, swaps, and other financial derivatives which occurs each and every day. Just foreign exchange markets alone trade $4 trillion a day in currencies and derivatives based on currencies. Constricting this torrent of gambling and redirecting these flows of money and credit into economically productive activities - such as ameliorating and solving global climate change - is the issue that will decide whether humanity survives as a species in the next two decades. So $2.5 billion to deliver to Mars a hunk of metal that can move on its own, is just chump change compared to the mind-boggling waste, misallocation, and abuse of society's monetary and credit mechanisms by the banksters.
Obviously, there are no political leaders in America who understand these issues yet. How our political leaders handle this area of science and technology is a key marker of where humanity stands on the path of progress and survival. The Obama administration's record here is arguably even worse than Republicans. As the article on the Curiosity landing by Space.com notes, Obama's 2013 federal budget request in February forced NASA to abandon plans for follow-on planetary missions of similar scope and scale to Curiosity.
This request cut NASA's planetary science efforts by 20 percent, from $1.5 billion this year to $1.2 billion next year, with further cuts expected in the coming years.
Much of this money will come out of the agency's Mars program, which sees its funding fall from $587 million this year to $360 million in 2013, and then to just $189 million in 2015.
In an plutocratic oligarchy, you really don't get any decent political choices. So, savor the triumphs that we are allowed. And safely placing a massive robotic probe on Mars is certainly one of those triumphs.