If part of the job of a supervisor is customer service (both internally and externally) then shouldn't the testing and interview for that supervisor position entail loads of questions about the candidate's ideas on customer service?

I guess I am just puzzled as to why the supervisors in the public sector are not tested for "likes" and "dislikes" in the workplace sorta like those personality tests.

Interpersonal skills should be a mandatory trait for a new supervisor. It should be tested during the interview process and there should be questions about it.

You can teach someone to write. You can also teach someone to answer a question to pass a test...but it is harder to teach someone to how to read another person.

And now that I'm on a roll...what about those in management not versed in management skills?
Shouldn't these positions require some sort of training BESIDES years of experience. Remember, just because you can do the job, doesn't mean you can lead and manage.