In my view, ageism is caused by line managers who feel they might not be able to manage highly experienced employees. They are frightened of mis-managing them, because with age often comes the ability to become extremely difficult if improperly managed.
If you mismanage someone with less experience, it is easier to get around the problem you have caused. On the other hand, if you mismanage a highly experienced person, and they start getting difficult, you will have a serious problem on your hands.
Managers therefore tend to prefer those who are less capable of giving them a hard time when mismanaged. It's down to simple job protection, and ageism is often a tacit admission of poor management ability.
Logistics News International