It even can run as Xen dom0.
Well, that's software developer-led cowboy coding for you: prioritization based on weekend impulses rather than user-driven urgency. Also, the hobbyist and volunteer excuses don't fly because a professional effort with a saleprice of $0 has to compete with non-free and is subject to forking and loss of interest if it founders or stalls. Also, I don't think there are enough NetBSD devs. It's main users are some ISPs for network infrastructure IIRC.
BTW, FreeBSD doesn't even run usably on RPi4, it boots and that's about it. RPi3 support is somewhat better, but still worse than RPi2.
I hope all FOSS OSes, including Linux, get and stay organized and productive, but not heading toward a greater unbalanced power law distribution (pun unavoidable) monoculture where only Linux dominates, because then we're in real trouble.