The koban system and shinuchi system are not perfectly based on ability, so another reason is that it is difficult to handle "one who has become suddenly popular" or "one who has been popular since his young days."
香盤制度・真打制度は完全な実力主義でもないので、“急激に売れた人”“若い時から売れっ子になった人”に対する処遇が難しいというのも理由の一つである。