That’s your opinion and you’re entitled to it. I think you’re wrong, personally — in venues where he has limited time to make a point (debates, TV interviews, etc.), he needs to focus on the topic at hand rather than waste time reciting his biography.
When he is at liberty to speak at more length, he does mention the fact.
There’s really nothing that’s more important for him to speak about to gain support than highlighting the serious and extensive experience he has obtained that makes him the most qualified for the office. Perhaps you forget, but most people watching the GOP debates only know that Fred was an actor on Law And Order. Maybe his problem is he doesn’t even realize that.