Professor: Obviously, this was a very difficult sound to pronounce. Not Latin, Greek, or even Sanskrit uses it. It does not occur outside of the proto-Indo-European language.
Student: Why did they use it?
Professor: They didn’t.
Student: I mean the Indo-Europeans — if it was so difficult to pronounce, why would–
Professor, interrupting: Why the hell does anybody do anything?!
–Etymology class, Hunter College