WHY SO DAMN MANY LANGUAGES?

In a comment thread at Oh, For a Muse of Fire!, I ran across a paragraph that so delighted me I had to share it here, with the permission of its author (who is also the prize-winning author of a number of sf/fantasy novels), Jo Walton:

I can also remember—when I was too young for school—trying to read a book of sermons in Latin, and discovering that there were more languages in the world than just Welsh and English. I can remember thinking that surely, two would be enough for all sensible purposes?