Why aren't MTX global?

Why do MTX have to be linked to a single subaccount?

How can Fortnite do this but you guys can't? How can Overwatch do this but you guys can't? How can Diablo 4 do this but you guys can't? How can Roblox do this but you guys can't? How can Dauntless do this but you guys can't? How can Rocket League do this and you guys can't?

The list goes on and on. Ii fail to understand how we can't have a global microtransaction system where I can use digital items I purchased on any of my linked subaccounts just because of some arbitrary rules (Im not talking about Sony).

I have been on support's queue for 2 months trying to get an MTX transfer to another subaccount because I dont use my other subaccount. Another can of worms is twitch drops, they automatically go to subaccount B instead of subaccount A for some weird reason, am I going to have to waste Customer Support's time every single time a twitch drop goes into the wrong account?

Just let us use/purchase MTX on any subaccount and use them wherever we want. You will be saving yourselves and us a lot of needless headaches.