Edit: even if the Nvidia blob were used, it would (i) be a big departure from Mesa architecture and infrastructure and (ii) it would be illegal to distribute it. Nvidia could also introduce an arbitrary amount of protocol madness to make accessing the firmware blob as difficult as possible.
Fortunately Nvidia provides all their drivers free of charge on their website, so it shouldn't be hard to download and extract it at install time?
Not really. Having a closed-source on-card firmware blob but linking it with an open source kernel-side driver would have so many benefits, first of all not needing to depend on NVIDIA to keep up with upstream changes and stuff breaking at every kernel, xorg or whatever upgrade.