Who cares if languages become extinct?
ultrasaurus.com
ultrasaurus.com
(Okay, I confess that I've taken liberties with the original, which is not about computer languages at all, so you should all go read it. But I'm being serious: This really is the argument. And it's a pretty good argument, though it's a little stronger when applied to thousand-year-old human languages than to twenty-year-old computer languages.)
For a more poetic take on the same thing listen to Wade Davis: http://www.ted.com/index.php/talks/wade_davis_on_endangered_...