Why do the libraries carry DVDs?

There is an editorial at Palo Alto Online titled “Why do the libraries carry DVDs?”

The editorial opens: Let us assume that stocking DVDs is a proper function of public libraries.

(I strongly disagree with that since supplying popular movies has nothing to do with literacy, education, citizenship, etc., and there are multiple low cost rental possibilities available to anyone. But, for the sake of argument let’s assume that it is proper.)
Editorial continued here.