ser v estar - again!
Why does your job use ser ie mi padres es un médico but to be retired uses estar ie Mis padrés están jubilados?
4 Answers
Usage Examples: Ejemplos de Uso: 1- Mi padre es medico ( Mi father is a doctor.)
2- Mis padres estan jubilados. ( My parents are retirees.)
3- Mi padre es un jubliado feliz. ( My father is a happy retiree.)
4- Mi padre es un jubilado, que tiene 70 años de edad. ( My father is a 70 years old retiree.)
Perhaps this article will help.

Mi padre es médico/Mis padres son médicos
Anyway, about the question:
Jobs are considered part of the classifying/defining facts about a person in Spanish, regardless of changeability. If you are a médico, it is a vital characteristic that defines who you are.
Being retired, on the other hand, is a state of being, or a condition. You might argue that being retired is something that classifies you too. After all, you've filled up forms that ask you 'bout your job. The thing is, you can use ser.
Using the old 'funeral' rule, when someone dies, you might go to his wedding and say 'he was a good man, teacher and doctor', but you sure as hell won't say 'he was a good man, teacher and retired'. You can, of course, also say 'he was a good man, teacher and a retired person.' Nothing wrong there. Thus, 'es jubilado' basically means 'is a retiree' or 'his job is being retired'.
Estar is more common in spoken language. There's a thread here with more info. Try using the SD translator with 'jubilado' and click the 'view posts regarding this word' to view loads more threads on the same topic.
And here's a quiz if you want to test your knowledge.
