In the oral arguments of King v. Burwell, Justice Ginsburg brought up the question of “standing”:

A plaintiff “has to have a concrete stake in the question,” Ginsburg said, interjecting almost as soon as Carvin began his argument. She noted that two of the plaintiffs had served in the military, one would soon turn 65 and be eligible for Medicare, and the fourth could qualify for a hardship exemption and not be required to pay the individual-mandate penalty.

Carvin countered that the lower courts had not raised a standing issue.

“But the Court has an obligation to look into on its own,” Ginsburg said. Carvin asserted that at least one of the plaintiffs did have standing before Ginsburg allowed him to move on to the merits of the case. (National Journal)

So what I want to know is, why doesn’t every taxpayer in the country have standing in cases like this?