[idlewords]

It couldn't, for a funny reason. Everything on a Shuttle flight could be automated except lowering the landing gear just before touchdown, which had to be done by hand from inside the cockpit.

There are rumors (that I've never been able to run down) that the astronaut corps insisted on this so the Shuttle could not be flown unmanned.

[gambiting]

And Buran(soviet copy of the shuttle) could and in fact did fly completely unmanned. In a way it's a shame the collapse of the soviet union killed that program, because a crew less shuttle would have been a huge asset to have.

[dabluecaboose]

I'm not surprised more people don't know about the X-37, but it's in effect the distillation of the Shuttle program to a very effective vehicle: Crewless, reusable, cheap, and effective.

Bureaucratic requirements and institutional jockeying largely ballooned the Shuttle into something it was never supposed to be.

[jaggederest]

Which is, regrettably, the same thing happening with SLS / Orion / Artemis