I believe Nintendo was right when they said it was a small group of Wii owners that were suffering from lack of blocks. Casuals either don't buy many or just buy a few VC games, and I would bet your average hardcore Wii owner doesn't buy enough to come near the 500 block mark.
You figure though that it would in Nintendo's best interest that we buy all the VC and Wii Ware titles we want. Is it worth losing sales just because non-gamers and casuals aren't really going to be affected. Hell the casuals probably wouldn't even care if the VC didn't exist. Customer satisfaction is important as well. Though you don't have to be a doormat, there is some value in addressing the issues of a sub-section of a customer base, even if their issue doesn't affect the majority.
And really it's all win-win for Nintendo money-wise. They get more VC and Wii Ware purchases from those that are running into space issues and they potentially get to sell some sort of hardware like a hard drive which, knowing them, will be priced to be profitable.
Do those you don't have the issue get turned off if Nintendo address an issue that didn't concern them? Not likely, providing Nintendo does it in a way that doesn't interfere with them (and I imagine it would take freakish incompetance to do that). But they can and will lose sales and piss customers off if they don't address this. So why not address it?
Plus the Wii has only been out for like a year and a half. It's not like we're near the end of the Wii's life and a small sample of really hardcore gamers are running out of space.