Why are there no AP assassin items?

Because AP assassins aren't flashy enough, so they don't get facebook montages made by 13 year old Weaboo Zed/Yasuo players.

That's all Riot cares about.

Ap assassins are Mages. there already in the game.

Killing someone from 100-0 in .3~3seconds is getting assassinated.

How do you make items specifically for ap assassins that aren't just better stat sticks for mages? The issue of ap is that the stat is universal and you aren't going to make many trade offs if you are grabbing them. At least in lethality's case an adc grabbing those items gives up attack speed, lifesteal, or crit in some form because you have to stack it. Make an ap item with say 60 ap some amount of pen and a passive. if that item is good it's gonna be on everyone until riot dumpsters it.

Remember frostqueens?

Is there really any issue with there not being any AP assassin specific ones? AD assassins and AP assassins would be equal if Lethality wasn't really strong.