This has been said in this thread before, and everything I've seen since bears it out: Big Cat is very loyal to Portnoy because Big Cat feels like Portnoy gave him the opportunity that's led to everything he has now (including significant $). I think Big Cat is a soft and possibly not very savvy guy who really believes in loyalty (someone has to teach him the old saying "it's not show friends, it's show business"). PFT thinks he does his best work with Big Cat and while he doesn't love Portnoy, he's not willing to leave Barstool without Big Cat, who'll never leave. PFT is also kind of an oddball personality -- I'm not sure there are a lot of other platforms that would let him fly his freak flag the way Barstool does.
I'm also not sure either of those guys is prepared to do the work that Simmons or others have done in order to hang out their own shingle. I don't get the sense that being leaders of men interests them.
In any event, this is all moot since I assume Big Cat's contract has a significant equity package with retention bonuses/requirements, so he'd have to get blown away monetarily for it to make any sense to leave (unless Penn Gambling's stock tanks).
Also, I expect these guys justify staying at Barstool because it's arguably no better ethically to go to ESPN, which bends over for the NFL every chance it gets and is offensively non-political, or Fox Sports, which employs Cowherd, Bayless, Clay Travis and other ne'er-do-wells who've said things just as offensive as Portnoy. And I can't imagine anyone else can pay as well as those two could.