Why does Devour have magic damage on hit as opposed to Physical damage on hit?

I'm just asking this question from a gameplay standpoint. I don't really understand the need for the magic damage on hit. I understand that the majority of the champions that benefit from the Devour upgrade are those champions that rely on auto attacks to deal damage, but by making Devour deal magic dmg on hit, you make itemizing against these fools a pain in the ass. It's already hard to itemize against them without the magic damage on hit, because most of the champions that benefit from Devourer also deal mixed damage within their respective kits. Let's look at few of the problem cases that abuse Devourer and or abused the old Feral Flare.

Deals true damage on autoattacks, while also dealing physical damage through auto attacks. Also, Yi builds which gives him the %current hp on hit. The magic damage is just the icing on the cake for Yi. He's literally doing true damage, magic damage, physical damage and %hp damage. There is no why to itemize against him in anyway. The same problem occurred when Feral Flare was strong, he can deal all sorts of damage so you can't itemize against him once he gets botrk/devourer.

Deals magic damage through her burnout, also has a linear skillshot that allows for her to do %max hp for every auto, also synergizes with so we can add %current hp physical damage and she has her Q and auto attacks. She also does every form of damage in the game, except true damage, but she makes up for that by doing %max hp magic dmg.

WW is going to get a rework I understand, but he's retardedly broken when old Feral Flare was strong and Devourer for the same reasons that Yi and Shyv are retardedly broken. WW deals magic damage on every auto through his passive, while his q does magic damage and %hp damage and physical damage through auto attacks and of course.... . Also WW has hard CC which applies on hit effects which also deals magic damage, plus the BOTRK procs and on top of that.. the magic damage from Devourer. Talk about holy shit impossible to itemize against.

There are many many other champions that are also almost impossible to itemize against due to devourer. that I didn't include ( to name a few. From a gameplay stand point, it makes for a frustrating experience to play against. You feel useless and helpless because you don't know where to start to itemize. I'd like to see devourer deal physical damage instead of magic damage so that I can itemize effectively against these auto attacking giants who end up murdering me and my whole team because we can't itemize against them.