Or we could take all that money and dump it directly into R&D.

If the government shit canned NASA tomorrow, and took that money and pumped it into the project Google is doing on self-driving cars wouldn't the world be a better place? Space is great, but how many lives could be saved by implementing self-driving cars nationwide?

Or took all that money and pumped it into computer science R&D. Or biotech R&D. Or nanotech R&D.

The argument for NASA often boils down to an argument for R&D, and there are a lot of more efficient ways to fund R&D than spending a bunch of it on non-R&D type stuff.