The differences between a manned and an unmanned vehicle are enormous. The Russians were never able to get their space shuttle clone (the Buran) to be able fly manned. If a vehicle isn't designed for it, you can't just add it on later.
Besides, the Russians can carry astronauts to space for comparatively very low cost (shouldn't we take advantage of this?), and there are several commercial companies working on manned flight programs.
If the government is going to work on manned spaceflight again, it should be for deep space, not low-earth orbit.
It wouldn't surprise me a bit if this "Unmanned" vehicle could quickly be configured to become a "Manned" vehicle(perhaps it already is). Despite the black hole this country seems to have fallen into, it's doubtful the U.S has left itself to be completely reliant on the Bolsheviks to get astronauts into space. This program must carry with it an enormous, yet undisclosed cost.
RE: "Parachutes can be self-guided and GPS controlled."
REPLY: The spacecraft and its cargo, and, most importantly, any passengers, remain at the mercy of local wind gusts and fast moving, unexpected weather systems. Parachutes may be a backup, recovery landing method in an emergency, however, for true progress in space flight a power-controlled, human-piloted spacecraft would need to be developed.
RE: "If missiles can land very close to the intended target, then any space vehicle could also do so. "
REPLY: For many of today's current and near-term requirements, this is true. However, the general public is not interested in business transportation or recreational travel whose landing sequence resembles the drop zone of a clown fired out of a circus cannon. I'm thinking of a distant future, a world whose advancement and technology permit casual space flight, similar to how humans now enjoy recreational aviation, which is exploration and business and family travel in the atmosphere, a mobile activity analogous to how people came to enjoy recreational automobile driving, which led to further exploration and travel on the surface of the earth.
For recreational, close-orbit spaceflight to come about in the next level directly above the atmosphere, spacecraft will eventually require a human-piloted, powered-controlled landing on an airport runway, or to be more accurate, a spaceport runway.
RE: "[…] the GPS guided chute can get it to within a dozen yards or less of the touch-down zone."
REPLY: This, still, requires numerous people and enormous air and ground resources to recover each and every spacecraft and is focused on the NOW requirements. Think, "Honey, I'm going to take our [spacecraft] into low-orbit tomorrow for a flight over Asia. I want to show the twins how the Tibetan plateau looks like for their geology mid-term exam that is coming up next week."
Parachutes can be self-guided and GPS controlled. Not knowing what it's used for, I really couldn't say if it's really necessary to have a winged, wheeled vehicle, but I am confident that economical return to Earth missions without fixed wings are very possible. If missiles can land very close to the intended target, then any space vehicle could also do so. And then the GPS guided chute can get it to within a dozen yards or less of the touch-down zone.
RE: “Most space missions don’t require bringing a spacecraft back to Earth, and the space plane makes no sense for them.”
REPLY: What? You mean we should continue to send numerous men in ships and aircraft, supported by enormous ground tracking stations, to locate and pick up a parachuted spacecraft?
A piloted or remotely controlled spacecraft that can make a normal, self-controlled landing on a typical runway is actually a momentous step forward. The Jetsons lifestyle must eventually arrive, otherwise we will continue to require huge, earth-bound resources and to depend upon the wind and gravity to retrieve spacecraft. Unfortunately, under these conditions, spaceflight will remain the province of the military or very large corporations.