Why HMS Pioneer was scrapped after a short career

Why was HMS Pioneer scrapped after only about ten years instead of being placed in reserve?

She was a specialized support carrier whose conversion was not worth the cost, and her light-fleet hull had been built for a short wartime service life.

Pioneer had been completed as a support carrier, and converting her to a different operational role was judged too expensive. Light-fleet carriers were also emergency wartime products designed for rapid construction and comparatively short service lives.