Why don't certain abilities like Caitlyn passive and Kennen W work with Guinsoo's Rageblade?

Before you make your opinion, please read the whole text through because I may have covered your point.

Alright, so if Vayne's w, whose text is "every third consecutive attack or ability against an enemy" works with Guinsoo's Rageblade, what is stopping Caitlyn's passive and Kennen's W?

Caitlyn "gains a free headshot every six basic attacks" and "every 5 attacks, kennen deals bonus magic damage ". Purely from the text of the abilities, disregarding visual cues, and putting on hold the true definition of a "stack" each of these abilities hold the same basic formula and meaning: Attack X number of times and your next auto will do extra damage. And with Guinsoo's Rageblade text being "every other basic attack triggers on-hit effects twice", it would seem that each of these champion's passive abilities would benefit from the item.

However, it is clear that Caitlyn passive and Kennen W are not treated to be "on-hit" effects. Which brings us to the definition of on-hit. According to leagueoflegends.wikia.com an on-hit effect is a bonus effect for a basic attack, and if it is parried, blocked, blinded, or cancelled by any means, does not occur. In testing, this appears to be true for all of the above abilities.

Next, we have the idea that Vayne's W is consider an enemy "stacking" effect, as opposed to Caitlyn P and Kennen W being considering a "self-stacking" effect. Why the two would change the result of their interaction with Guinsoo's is not rationally clear to me and brings to light that there is no real telltale sign from the language of the descriptions of these abilities. If this is the intended reasoning behind why Guinsoo's does not work, the wording of these abilities must be changed to more accurately represent what types of effects they are.

Additionally, if this was intended for the purpose of balancing the champions, I can assure you, that Caitlyn would not rise to power simply due to the nature of her passive and how well it is complimented by critical strike damage. Kennen's on-hit path would likely also not begin to dominate, as his damage scaling and ratios have been gradually adjusting to better support AP Kennen.

Hopefully I'm not missing something painfully obvious, and would love to know what everyone else thinks about the item.

I'm just tryna have fun playing on-hit builds and I'm disappointed that it doesn't work the way that it seems like it should.