It boils down to the old adage: "If it ain't broke, don't fix it."
This is exactly right. I was playing with the last lot of RHEL7 betas - the biggest issue I had was that ethernet adapters would randomly fail to start - and systemd would not give any details as to why. Each time I had to log in over a serial console, stop networking, disable the profile, enable the profile again, and start networking. This would work perfectly - until a random time when rebooting later on (and not every reboot) where networking wouldn't come up again.
This is not what admins need - randomly failing network connections. This is also a problem that was fixed decades ago - until systemd causes it again.
Lets ignore the problems with new aims to recreate consoles etc in systemd / userland and ignore / disable the kernel ones. Because that's a great idea *cough*