I work at a company that fired an older employee who was pretty worthless. She then sued the company for "age discrimination". She did not win, but it was still a PITA for the company to have to bother with it.
Years ago I fired an employee for a very serious offense. (today it would qualify as a form of identity theft).
We promoted her assistant to replace her. The woman we fired was 54. Her assistant was 21.
The fired employee waged a THREE YEAR legal battle for reinstatement and back pay. Which she eventually WON!
Based on little more than the fact that she was over 50 and her replacement was 21.
Nevermind that her replacement was efficient, conscientious and good with customers. Everything she was not.
It made my head explode. Fortunately I had moved on from the company and no longer had to manage her. I was 33 at the time.