First, correcting myself: the original version of Sacred Healing functioned thusly:
“You can spend a turn attempt as a full-round action to grant Fast Healing 3 to all living creatures within a 60-ft. burst.
The fast healing lasts for a number of rounds equal to 1 + your Cha modifier (minimum 1 round).”
That's precisely the kind of thing I warned against. Healing is universally useful, and it's not good to be able to turn what's normally a niche ability into a universally useful one. Well, not unless your goal is a strict power increase for the class in question.
As for the ubiquity of turn/command undead among clerics, even those that seemingly doesn't have anything to do with undead, I think it's part of a thing I'm really not particularly happy with regarding D&D's standard treatment of gods and their clergy which is their attempt to be universally applicable religions. I'll use the Forgotten Realms as an example here, but AFAIK Greyhawk works similarly, and it's pretty much the D&D default (and it has also spread to Golarion/Pathfinder).
Take someone who worships Sune, the goddess of love and beauty. They are expected to take care of their looks, to help others do the same, to support couples in love (including supporting marriages for love over those for duty), create or commission works of art, and so on. And if you're a good enough Sune worshiper, after you die your soul will end up in Sune's planar domain.
Or take someone who worships Helm, god of guardians. They are charged with, well, guarding things. I imagine it also includes building defensive works. At the end of the day, if you are a worshiper of Helm and stayed at your post when told to, Helm will claim your soul in the afterlife.
Or maybe you worship Gond, god of crafts and invention. You'll probably work in a crafting profession, where you will seek mastery of your craft and hopefully invent new imrovements of it. And in the end, Gond will take you to the great workshop in the sky.
The common thread there is that even laity is expected to have a single patron deity, and mostly forsake all others. Maybe the Helmite will give an offering to Sune when wooing a person to whom they are attracted, and the Gondsman might pray to Helm to help defend their workshop if they're being robbed, but overall they are expected to pray to and sacrifice to one god, and in the end go to that god's afterlife.
It is that connection to the afterlife that makes clerics good at dealing with undead. All gods have an interest in seeing that the afterlife runs properly, and undead interfere with that.