Because a lot of three letter agencies demand these hardware backdoors exist, and AMD has no will to fight them on it. They announced intent when they released

Because a lot of three letter agencies demand these hardware backdoors exist, and AMD has no will to fight them on it. They announced intent when they released Ryzen to "look into" disabling their ME (they call it the PSP), and then six months later made a backroom comment that it is never going to happen.