Technically? Support wise? It adds unnecessary complexity. We are using controlled environment to rule out most stupid troubles and to save time. Stupid troubles can be big time wasting elements.
Most of the distributions usually don't have developers & maintainers for core components. They ship vendor prepared firmware, our firmware, pure mainline ... or something in between. Best working kernel is vendors (when hw is released) while mainline always remain in pretty raw state also after years. We keep that operational, starting with some features, adding more. Some are coming from mainline, some from our labs. Some might never come to the main Linux tree and we could maintain features nobody else. And a lot faster then mainstream. Mainstream turn around is slow, time consuming, commonly poorly tested. Most of troubles we have in stable branches are coming from mainline, from that "doesn't matter" space.
Morally?
If you are asking for support on 100% my personal expense - my time is most important value. Not yours is. Technical support for Armbian users or even supporters that help us pay the bill they are generating to the technical infrastructure (electricity) is on the edge of possible. We can't finance people out of that. And since we have very limited resources, 3rd party Linux users are simply always last to be serve. There are many things you have reported or we find but are not fixed yet. First sorting out that, then 3rd party problems. Fair?