Something I don't understand

More than one person has told me that they're at universities that simply ignore book chapters when it comes to tenure or promotion--that these chapters somehow don't "count" as refereed publications.  I admit to being somewhat puzzled by this.  I've had chapters appear in books published by both commercial academic and university presses, and all of them, as far as I can remember, went through peer review.    Now, it's quite likely that a chapter in an edited collection won't receive the same kind of concentrated attention from a reviewer as would a stand-alone article; after all, the reviewer may have to evaluate over a dozen contributions in one go.  Moreover, given how such collections are assembled--articles solicited and/or accepted provisionally from an abstract, then approved on receipt--it's true that editors may well feel uneasy about jettisoning something, although I seem to recall some articles being cut loose from at least one of the collections in which I appear.  Then again, I've received reader's reports on journal articles that were even less useful and informative than the ones I've received for book chapters.  Sometimes, that "concentrated attention" is not so helpful.   So where did we get the idea that edited collections didn't go through the usual peer review channels?