People get a rotator cuff impingement for different reasons. In people younger than 25, it’s often caused by using your shoulder too much, or by trauma.
But if you’re over 50, it’s probably due to general wear and tear on your shoulder over the years. And the injury is more likely to go beyond a “pinched” tendon, and could end up as a partial or complete tear.
Sometimes, an injury, like falling, can also cause an impingement.