First of all, I doubt the number of people who care about this issue is in the millions.
Second of all, it wouldn't go away no matter what he showed them. If someone showed a judge the vault copy of his BC, the birthers would find some way to argue the judge was in on the conspiracy and not to be trusted. If he posted an image of the vault copy on the Internet, some anonymous guy with a phony Ph.D. would write a 200 page treatise claiming to have "conclusive proof" it was a forgery.
Even if he could, by some miracle, convince the entire birther fringe that the BC was geninue, they'd be filing lawsuits claiming he is ineligible because his Father was Kenyan, or because he lived in Indonesia, or some other half-baked nonsense.
The simple answer as to why he hasn't done more to satisfy the birthers is there's no satisfying them.
WTF is it with you RomneyBOTs? Why the love for Obama?
Why did you work to put him in Office and defend him now?
If two states are changing their election rules because of this issue, I think it's safe to say that "millions" are wondering about it.