In the US, Disney brands itself as family/kids entertainment which often is associated with being anodyne with things such as sex, language and graphic violence so I think there's a premium set on keeping such things strictly separated from Disney branded platforms. Having Hulu as another platform not explicitly branded as Disney allows them to split the content and not have parents angry that little Billy saw something inappropriate because they didn't set the parental controls as they should have.
Then why is Disney + in other countries allowed to put it all under one service and not mind being associated with stuff like "Pam and Tommy"?