I was thinking more along the lines of knowing how many owners the player has had, whether it came from a reputable source, etc.

Just as additional assurance that it's not stolen. For example, if the player has no sled, or a sled with all the wires cut off, and the seller won't say where it came from or why it's missing the sled, then buyers will have fair warning.

It doesn't stop a fence from lying about it, of course, it's just another layer of comfort.

I'd probably put something like that under the heading of "suggested" as opposed to "mandatory".