NASA is a government agency and as a government agency it is used as a vehicle to implement the general purpose of the government.

To put a different example of the point. If the cheapest way to launch items into space was for NASA to buy rockets off Russia, would that be what it would do? No, because government policy includes independent launch capacity.

NASA isn't a private company, it is a tool of government and as such it can have have a wider role in society then a compariable private company will have.