Why is a prisoner someone who is in prison but a jailer isn't someone who is in jail?

Answer: Technically both are in jail. The jailer is more of the guard than the actual inmate that has committed a crime but, some people see them as criminals to because they are the one locking them up from the public due to their actions. Most punishments now a days are being looked at as to strict or harsh.

jailers put people in jail or jail them

Explanation:

prisoner is just a name given to someone to describe what they are, the same is with jailers they jail people or watch people in jail this describes what they do and what they are.

I've never thought of it that way unique question.