Yeah I don't think most studios are run with the idea of making the model the most possible money.
The studios are run to make the studios the most possible money.
Letting their performers have contact with clients in ways that aren't monitored (and profited off of) by the studio, are obviously going to be huge no-nos for them.
Obviously the worst fear of a studio, is for a model to garner a personal clientele and then leaving the studio (and taking her clients and their money with her).
@Sansa hit the nail on the head with the Skype and twitter shows though.
Dips in camscore mean the models earnings will take a hit, too.
Studios have no use for offsite payment, and why would they let their models accept less money for the same show they could provide in a private at 60 tokens per minute on MFC?
And if the studio ran twitter accounts for their girls, it would be a whole lot of tracking people down for pictures/content to update, and endless hours doing grunt work, with little return (since most social media platforms banned porn/18+ content, most performers are perpetually shadow banned anyways).
That's just a studio, c'est la vie.