You'd need to take a too narrow a view to get stuck on this for all systemd's adoption. Obviously SystemD being developed by Red Hat engineers such as Poettering, we saw it first coming from the Red Hat/Fedora side. But this does not then explain adoption by other Distributions like Debian or Ubuntu. I think it more likely that there are actual real-world reasons to explain this and I'd put this back to it being for the Enterprise and not for the expert user.
Obviously there are many distributions that do not use SystemD still, and some branches of both Debian and ubuntu that do not use SystemD.