Enterprise vendors have gotten better at locking in customers on multi-year contracts which takes away some of the biggest upside to chipping away at the market. Often a challenger will come in and snag a few smaller deals but the Monopoly has a plethora of options to swat it away - rev up their larger more experienced product team to compete, lobby for regulation, poach from the challenger, acquire the challenger, tank prices in the one area the challenger has traction, and much more.