Because minorities die first, of course! And that comes straight from the Department of Justice so you can believe it, okay? Muckraker has the story:
John Tanner, the chief of the Civil Rights Divisions' voting rights section, ....showcased his own analytical skills, telling an audience that voter ID requirements actually disproportionately affect whites.
Tanner explained that "primarily elderly persons" are the ones affected by such laws, but "minorities don't become elderly the way white people do: They die first." So anything that "disproportionately impacts the elderly, has the opposite impact on minorities," he added. "Just the math is such as that."