To be fair, the Falcon 9 similarly discards its entire second stage.
I really wish they'd have boosted the Shuttle tank to stable orbit and used it for space stations.
One would make a pretty serviceable space station.
100+ would make one hell of a space station if you designed them to be strung together.
Some early NASA concepts: http://www.astronautix.com/s/stsexternaltankstation.html
If you're wondering about practicality, Skylab was a Saturn V tank. Unlike the external tank suggestions, Skylab was built on the ground and never had fuel in it. But it was basically the same structure as the Saturn's third stage. Like ISS, Skylab had some micrometeorite shielding outside of the main tank.
https://en.wikipedia.org/wiki/Skylab
More recently, Nanoracks has looked at refurbishing ULA's Centaur upper stage into a habitat. Like the Shuttle, Centaur runs on a H2 + O2 cycle. Their plan is to lift an equipment kit onboard the Centaur. They'd cut a hole after the end of the mission and use on-orbit welding (not mature yet) to install all the floors/decks/airlocks.
And the Shuttle itself was reusable, but that's sort of besides the point, as that's a space-plane, not a rocket used to bring things into orbit. Whether capsules or space-planes is a better concept for the spacecraft itself is a different discussion altogether.
The per kg cost to orbit of Falcon 9 launches is an order of magnitude less than it was for Space Shuttle, so credit should be given where credit is due.