Cena is the last WWE independent contractor (refuse to call them employees because they're not), who broke through like Austin and Rock did and you just know that behind closed doors it eats Vince alive when he thinks about it. he truly thinks that he is entitled to a majority percentage of his independent contractors earnings for life. although Cena did break through for the most part, he still bends his knee to Vince in many ways and still doesn't own the intellectual property to his legal name like Austin and Rock do. so Vince still gets a cut of everything Cena does outside WWE.
that is why as many already know, that WWE has a 50/50 booking policy the last 10-15 years or so. Vince will not allow any of us independent contractors to ever get enough momentum and outside interest to even the playing field the way that Austin and Rock did.