Not understanding why they exist is the first error trying to sell to enterprise.

Seeing how .Net is being sold to enterprises without such libraries I would say that they exist because business happily buys into any promise that something increases productivity even if that is just salesmen's lies. But it requires good salesmen not good engineers.

Actually it does have many of those libraries, they just come with a different name, or in commercial only form, without the FOSS variants from Java.