Hoarding by Marquee Art Museums

In this recent episode of his terrific podcast, Revisionist History, Malcolm Gladwell starts to explore a topic that has always bothered me: the fact that marquee museums typically have vast storerooms of artifacts that are seldom, if ever, displayed. I don't want them to be sold to private collectors, but wouldn't everyone be so much better off if they were viewable in second and third-tier museums?

(I say "starts to explore", because that is the intro to the episode, but then it segues into an examination of hoarding behavior, the NY Met merely serving as an attention-grabbing example.)