Why does Nocturne's passive scale with AP?

Cause Riot does that on champions to keep the balance. If they made it all one way or another it's usually too overpowered.

For Wukong its cause he's an old champ, and cause old triforce used to have some ap (goal was to make him use all stat).

But yeah, its stupid to not have changed this since.

Baron buff, Guinsoos and versatility inbuilt options.
Mostly Baron - similar reason etc have AP ratios on Q.