The value is as a relic of the cultural recent past, not necessarily as great art.  

Why would the Oriental Institute keep yet another Babylonian seal?  Why does the Field Museum have on display (as I recall; it's been a while) fish-skin boots from a village in Iceland or Norway?  Why does the Indiana State Museum have an old mechanically agitated washtub?  If greatness is the criterion, then "hardly worth saving".  But museums are not for greatness.