These aren't problems for everyone but I think they should be front and center when suggesting it.
5k stars on Github, and lots of activity. Seems very interesting!
They don't much contribute to it directly, but they have gone out of their way on a few occasions to avoid breaking it or to make it easier for headscale to implement some things (like the new encryption scheme for communicating with the control server).
I imagine they don't see it as much of a business model threat, since it has no commercial support, requires having somebody your organization run and administer it, it is single tenant, not multi-tenant, so not really suitable for AWS to take and use to outcompete Tailscale proper, etc.
The people most likely to use this are the ones too concerned about security to use the official (Tailscale-hosted hosted) control plane, or people/orgs that simply cannot reasonably afford Tailscale's pricing model. In either case, they were not really customers in the first place.