Truth is they won't, even in CN it's not like that. They are there because each star added will bring a boost to overall team stats, not because they will be reclaimable from those scrolls... Ex: the last scroll in CN is for meme ninja like moegi and udon but they are not reclaimable from there.

I agree though that as these ninja hardly show up in events at times it would be nice to have them cost coupons through the scroll feature, even some ninja you could earn for free like hashirama Oasis could get players to spend on.