Politically, space is not important. NASA is an $18B annual bargaining chip to buy off various constituencies. That's not surprising, in fact it is typical. It has led slowly and inexorably to a federal agency much like any other federal agency that is not directly accountable to the voters (ie, all of them). Absent other influences, this leads to one way of thinking:
1) People who fly are people who die. The general public is not interested or wowed by spaceflight, they could care less. Only bad things can happen for politicians when astronauts fly. To a lesser extent, this is also true of multi-million or -billion dollar satellites and probes as well. The ideal NASA program from a politician's point of view is one that spends the maximum amount of money on the minimum amount of flights. The result: massive overhead is designed into the programs. Overhead doesn't kill anyone. It doesn't do anything, in fact.
Absent other influences. There are always other influences, but until recently they have been small fries. It took enormous political capital to get Shuttle up, and no one is going to get behind something like that again. So what is currently leading the push toward commercial?
Former NASA administrator Michael Griffin saw it clearly when he railed about "the Gap" after the Shuttle was sunsetted. He reacted the wrong way, as do all politicians, by grasping tighter to the status quo and assuming he could steer funding and/or change the way a massive bureaucracy gets things done. But his assessment of the problem was correct. It is politically embarrassing to buy things from Russians.
Faced with this nationally important strategic fact, and a commercial industry ready and willing to come to the rescue, it seems likely that on the order of $5B will finally be skimmed of the NASA pork cream pie to actually get something done. The NASA boondoggle will still get their $5B annual to work on paper rockets - this time called "heavy lift vehicles" - that are not strategically important to most political careers. They can overrun the cost and schedule on these while never flying anything useful until the next sellable scam comes along. But the agency will finally be doing something useful with a real chunk of its cash, and that's a good thing.