A couple of you asked this question: "What happens to the health of all those 'wild horses' in the country that don't have anyone to clean their sheath for them?"
Isn't that like asking, "What do wild dogs (coyotes, wolves, and foxes) do about fleas?"
They get by, of course. If there's discomfort, they simply have to live with it (or die with it).
I've had geldings before, and had never even heard of the procedure of sheath-cleaning. Obviously, they got by fine without it. I learned about it because when I first got Blue, he kept rubbing his behind on any surface available. So I went to Google (my eternal source of information) and did a search about horses scratching their butts, or something similar. Yep. I did. I learned that, since he couldn't scratch where it really itched, he scratched his butt.
That's how I found out the source of his discomfort.
Now where else could you learn all this useful stuff?