‘Managers get the things done by other people.’ Does a manager need to work himself?

A "manager" is a person who "manages". It may sound easy that managers ONLY assign jobs to other people, but in reality managers have to work harder to make sure that the jobs assign are on time and the output is as per requirements. 

Different managers have different ethics of working but nevertheless the most effective ones are who can get the work done. Saying that Managers ONLY assigns jobs to others is half the statement. The complete Statement is "managers assign jobs to to others to make sure that the remaining things are in sync with the Department/ Organizations requirement". 

It is a different issue who uses what ethics to get the job done. 

yes manager need to work himself