Being a manga author is creative, artistic work. Even in Kubo's case there must be something creative going on inside his head. I doubt Bleach has been able to satisfy that for a long time now. The artist in him must have been yearning to end Bleach, no matter how nicely consistent livelihood it brings him, in favour of something that would again make him feel like an artist, not a factory worker. He just doesn't have the guts to do it - which actually does sound like a pretty Japanese thing.
Regardless of what Bakuman claims.