If everyone has their own forks that's a lot of wasted effort compared to everyone having their own packages but using shared distribution infrastructure.
And it's the exact reason why unification through systemd makes sense.
Actually one of the biggest problems with systemd is its refusal to cooperate with other system components. Need a binary log format? Let's write our own! Need a database? Let's embed our own! Interoperate with ConsoleKit? Nah, we'll just reimplement a replacement.
I don't know about the rest, but AFAIK, ConsoleKit wasn't maintained anymore.
Given that the second most prolific committer to the ConsoleKit git repository is a certain Lennart P. it is reasonable to assume that the systemd people did not decide to implement logind from scratch because of NIH syndrome.
Would not the traditional option be for the systemd proponents to form, and then demonstrate that their alternative works? Then people could move over at their leisure?
There were so many technical proponents of systemd among distributions that it's now used by most of distros.
This is not true, unless you happen to have too many dollars to spare. Also, Windows can also be forked, by distributing patches instead of binaries.