The majority of Linux distributions out there seem to be over-engineering their method of distribution. They are not giving us a new distribution of Linux. They are giving us an existing distribution of Linux, but with a different distribution of non-system software (like a different desktop environment or configuration of it)
In many cases, turning an installation of the base distribution used to the one they’re shipping is a matter of installing certain packages and setting some configurations. Why should the user be required to reinstall their whole OS for this?
It would be way more practical if those distributions are available as packages, preferably managed by the package manager itself. This is much easier for both the user and the developer.
Some developers may find it less satisfying to do this, and I don’t mean to force my opinion on anyone, but only suggesting that there’s an easier way to do this. Distributions should be changing things that aren’t easily doable without a system reinstall.
Ubuntu has significant differences from Debian so it wouldn’t make much sense to be able to install it as a “flavor” of Debian. However, *Ubuntu are pretty much already metapackages on top of regular Ubuntu. So instead of having different installers for each one, you could just make it an option during install and provide an easy means to add/switch other options later
Yes, if all *ubuntu variants were maintained by Ubuntu maintainers. But since that’s not the case, again, it would be complicated for releasing.
Many distros already offer window manager options when installing, but that’s inside the same distro, not bits and pieces of different distros with possibly different release cycles and dependencies.
One distro may not wish to be “absorbed” by the other.