I have no idea why they're still so popular. I can only assume people don't think about it rationally. I don't know anyone who drags DVDs around with them, so why drag around the drive?
Frankly, I haven't needed an optical drive in a laptop since booting from USB drives became practical a few years ago. (happy MacBook Air user here)
It'll be interesting to see if Apple fleshes out its Cinema display into a combined docking station and screen using the Thunderbolt port's potential. Add a DVD drive, HDD for Time Machine, USB/Firewire controllers, ExpressCard slot, whatever, using the PCIe channel in the Thunderbolt.