The money in shootfighting isn’t nearly as good as the money in pro wrestling, at least for the time being. It’ll be a long time before shootfighting and/or MMA reach the mainstream acceptance and money-making potential that, say, boxing enjoys. When Shamrock was in the WWF he was over. If he came back, he’d be super-over. But is he wrestling before thousands of fans across the US? No, he’s still shootfighting for groups in Japan like PRIDE and Pancrase whom nobody really cares about outside the hardcore MMA fanbase. Surely he’s done all he can do in the octagon?
And besides, Randy Couture would lick his arse royally.