Sister was an AF logistics Major. Adult onset allergies made her non deployable. She was medically discharged.
All medical and mental conditions which prevent deployment - long term - should be processed out. I do not count pregnancy as long term. However, child care IS long term and if it is incompatible with the job, should be processed out.
There was this Airman who was on number 5 at one of the base I was station at. She has never deployed in 10 years, then complain and got out of it when they attempted to deploy her.