Yes, on the one hand, each specific distribution doesn't have this problem because it can pick up everything it needs.
But for us, independent developers of small programs, the problem is truly stark: we can't afford to build our programs for every distribution. And we can't afford to waste time navigating all the idiosyncrasies of various package repositories, both technical and political (not all repositories allow easy access).
And we can't count on someone else packaging our work until we become incredibly popular.
Most people use the major distributions like Ubuntu, Debian, Fedora, Arch, alpine linux, void linux,… A build machine with VMs can easily take care of those.
> And we can't afford to waste time navigating all the idiosyncrasies of various package repositories, both technical and political (not all repositories allow easy access).
Most (if not all) package managers allow for custom repositories. No need to get access to the official ones.