Most adults lose flexibility in their hands as they grow older. This is often the result of neglect and misuse. In our tai chi school we often ask new people to try and use baoding balls.
This is usually quite telling. Baoding balls are 2 metal spheres held in the palm of the hand and rotated using the movement of the hand and thumb.
Often people are exceedingly inept. Their hands simply will not move adequately to perform the exercise.