This is an important question. There are apparently 196,839 known list items based on a query for instanceOf Wikipedia list item (CLAIM[31:13406463])
I tend to agree with Thad that these kinds of items aren't really what we want filling in WikiData. In fact replacing them with the ability to generate them automatically based on queries is a primary use case for wikidata. But just deleting them doesn't entirely make sense either because they are key signposts into things that ought to be brought into wikidata properly. The items in these lists clearly matter..
Ideally we could generate a bot that would examine each of these lists and identify the unifying properties that should be added to the items within the list that would enable the list to be reproduced by a query.
I disagree that this reasoning suggests deleting items about categories and disambiguation pages. - both of these clearly have functions in wikidata. I'm not sure what the function of a list entity is.