What do you mean reuse whatever is available? Non derivative distros are going to be using their own package manager and not just using some prebuilt package fo

What do you mean reuse whatever is available? Non derivative distros are going to be using their own package manager and not just using some prebuilt package for another system. But regardless, I agree, fragmentation isn't really a problem. It would be very rare indeed for some software to only work on some distro but not another. And if this was the case, you could probably change it with enough work (swap out libc or whatever).