Those 3 aren't popular champions at all though.. Riot always tries interesting skinlines with champs no one plays like the paper Anivia and Nunu, and then they act surprised that they didn't sell that well and these skinlines are never seen again.
We actually adjust expectations and performance benchmarks on a per champion basis. So if we say something like “Papercraft didn’t perform well” that doesn’t mean we’re comparing Papercraft against KDA. It means we’re comparing Papercraft Anivia against other Anivia skins and evaluating whether the core audience for that champion really liked it.