To all people saying "just install another hard drive", most people don't need or want another hard drive. Who wants more than 1TB in a laptop?
Wouldn't it be better to see some serious increase in power and battery life? I mean, there is room in there for another computer for gods sakes! The optical drive isn't worth it when instead the MBP 13" could become seriously powerful.
I don't think anyone is disagreeing with you here. It's just that as Apple has not (yet) removed the od, you might as well sort it as best you can yourself now with the Optibay, or OWC's Data Doubler.
The second drive option is not all about capacity, but rather flexibility. And yes, there still is A LOT of wasted space, even with the bulky bracket and second HDD, so yes plenty of room for extra battery gpu etc.
I personally think we'll get SSD standard on all MBPs on the next revision. Actually 'flash' chips ala MBA so it too can be thinner and lighter.