Because it works with nonfree drivers (in addition to free drivers). THAT'S NOT A REASON.

1. As I understand the reasons, I disagree with them.
2. Beyond that, these kind of reasons need to be discussed. This had not been discussed on the bug tracker, dev@lists.parabol.nu, gnu-linux-libre@nongnu.org, LibrePlanet wiki, or #fsf. It was only been discussed on #parabola briefly, on 2017-03-12.
3. The blacklisting was haphazardly done, and broke user upgrades (see #1243).