There have been attempts at that but little to no customers. [I am defining "customer" as someone willing to pay money for that work versus someone who will pay test time or patches.]
Customers for the most part want the latest X to work, but don't want anything else to change. And the larger the customer the more they want that lock in for longer times. So there are places still using and paying for 2.4.x kernel (and ancient gcc,perl,python) support but also will pay some consultant to make the latest desktop to work on it.