Currently, a blind or severely visually impaired citizen cannot distinguish between any form of paper dollar, be it one dollar or a hundred. This can lead to theft during employee-customer transactions as the disabled individual must rely on the honor system when handing over money.
Adding braille to the dollar bill would solve this problem entirely and would be very simple and fiscally manageable. There is no good reason not to make such a simple change. Even if it would take years for the majority of circulated dollar bills to contain braille, the change has to begin at some point.