Purpose of worker-id property for External Tasks

Hello, please tell me about the purpose of the worker-id property.
If I start multiple instances of the service (with the same worker-id and subscribed to the same topic), each of the instances participates in the execution of tasks. The execution of one task is not duplicated.
If I run several services subscribed to the same topic, but with different worker-ids, then they work in exactly the same way, each of them participates in the execution of tasks. The execution of one task is not duplicated.
So why should I make worker-id unique?

When a worker locks a job the name of the worker is the key used when the job is completed.

You should always give your workers different names because if you don’t you could end up with a situation where a workers no longer have the security that jobs will only be completed by the worker that locked it.