What is a manned space programme actually for?

Today President Obama announced that in his next budget he was going to cut funding for NASA’s Constellation Program, and with it the plan to send people back to the Moon. This is no doubt going to lead to a lot of noisy protest; but I can’t help wondering if it isn’t the correct decision, because I was never entirely clear on what, exactly, they were going to do when they got back to the Moon beyond a “well, gee, we’re on the Moon!” and we managed that 40 years ago. In fact, the story of the Apollo program contains a salutary lesson about the consequences of gearing your space programme totally around the simple goal of reaching somewhere: once you’ve got there, that’s it.
It’s normally around this stage of an argument about manned space flight that someone plays the “inspiration” card. But I can’t remember when I was last inspired – really, truly, left awestruck – by something an astronaut did. The most exciting thing that I can recall any of them doing in the last couple of decades is fixing up the Hubble Space Telescope three times, and the inspirational bit came from what Hubble did after it had been made even better than before. Most of the time the astronauts just head up to the International Space Station, stay in orbit for a few months, and then come back home again. They take the odd pretty picture, it’s true, but what’s their primary function? Yes, we get more data on the effects of long-term zero gravity on human physiology, but are they really doing anything that wasn’t being done on Mir 15 years ago? I can’t help feeling that – much as it pains me to admit it – they’re there just so the ISS seems like a bit less of an orbiting albino pachyderm. Either way I would bet a fair sum that more people currently know the name of a valiant little Mars rover than know the names of the current astronauts on the ISS. Because Spirit has done things.
From this, you might reasonably conclude that I’m completely against the idea of sending people into space. I’m not: I’m just against the idea of doing it on the cheap. If we’re going to revisit the Moon, and go on to Mars or near-Earth asteroids, it shouldn’t be just to commit the worst form of checklist tourism – to go just so that we can say we’ve been. It should be with a purpose – with the aim of actually doing something new and interesting whilst we’re there, or at least as part of a wider strategy of establishing a useful human presence in space beyond the tiny and impotent foothold we maintain at the moment. That would be inspirational. But I suspect that it would also be much more expensive than I think we’re willing to countenance right now – and, more importantly, probably beyond our current space technology.
But perhaps I’m wrong about all this. What do you see as the point of manned space flight right now? What point do you think it could have?