I don't think you understand how much Memphis values making Conley and Marc the faces of Grizzlies basketball for now and always. I doubt they ever let them go barring a request for a trade from either.
It's worth more to that franchise to keep their beloved players into retirement than to make an Ainge like move to try and jumpstart their inevitable rebuild.
It's a lot easier to make that kind of move when your franchise has decades of star players that have come and gone. The Grizz have nothing like that.