What's the point? Those who need it can reinstall it themselves, and those who don't need it don't need it, and Vista is perfectly fine for them.

I'm not arguing with that - it's true. But do you know how much Vista costs? Around $100 USD and up, depending on the installed version.
So why should someone pay for something they don't need? That's the most interesting part. What if I already have purchased software, and with that money, I could buy better hardware. And it's not just about Vista, but about any software; Vista is just the most striking and well-known example of consumer rights violations.