They aren't able to grow...
Dig this picture from the DC Public Library Foundation website... here.
The quote from that webpage is:
Libraries are not made; They grow.
Did you know that the four new libraries being built in the Anacostia, Benning, Shaw, and Tenleytown communities are NOT being constructed to put on additional floors at a later date.
The original library buildings, except for Shaw, allowed for additional floors to be added later.
This is especially disconcerting in the Benning community where a 1.5 level library will be dwarfed by coming development which calls for 6 story mega-condos.