No you don't have to buy a considerable amount - no one is making you buy games for the Stars, because you buy the games you want and they are included at no extra cost.
The VC clearly isn't ridiculously overpriced if people are happy to pay for it. They could've not bothered with Stars at all, or at least converting them to Wii points if they are making a huge profit on the VC.
I'll agree that the Stars catalogue, to date, has been poor in comparison to our Japanese friends.
No one’s making you buy them for sure but for me atleast I see them as part of the Nintendo experience when you buy their first party Nintendo products, and not something stuck in as an afterthought for free. I admit I'm particularly sour on the matter though as I have been looking forward to this scheme since it was announced early in the year - and I don't consider to 4:1 point exchange ratio to be particularly rewarding and as others have pointed out they've had much better offers than this before. This also isn't helped when you see Japanese equivalent getting a rather cool SNES style classic controller.

I disagree on your point about the price though. Just because something sells doesn't mean it’s not overpriced.