Just like the early days of commercial aviation
Commercial aviation originally made its first money by carrying mail on government contracts between different locations. It was this that allowed the nascent carriers, both in Europe and the US, to get passenger services off the ground, because they couldn't afford to compete with the railways at that time. This decision is in a similar vein, allowing visionary private sector companies a slice of government money for services rendered.
I think this is a pretty excellent move by NASA, although not without risk. Call it a subsidy, call it a handout, but this is how governments should get high risk industries and markets established in their countries.