Canonical have done most of the work for LXD (including directly employing the main developer for years). Until now, they've been doing it under an umbrella project that was specifically not Ubuntu focused (to quote linuxcontainers.org: "The goal is to offer a distro and vendor neutral environment").
Now they've moved the project directly under Ubuntu, why?
The answer to me seems to be that they still going to do development, but they will no longer try to support anything but Ubuntu (and really, my guess is it will go the route of microk8s and become snap only/first, so more of a middle ground).
And I don't really blame them for that - they're doing the work, they can focus on themselves. But it does mean there is now a need for someone to do the work to become the packager for other distros. That development has to happen somewhere else now.
That may well be this repo, it might not.
If you use commercially-led software, you have to trust the publisher to stay aligned with your interests for the entire duration of you using it. This might go okay, but it might not - and there isn't any commercial entity who won't start squeezing when they feel necessary. So why expose myself to the whims of someone who might flip at any second?
Of course, things may change at Canonical if I am no longer involved. That's a reasonable risk to think about and have a plan for. Some paranoia is constructive. One of the nice things about open source is that you can fork it if you want to. But to do so just because Canonical might in future take a different view than we have to date seems like its paying too high a price for that paranoia :)