The Hornets do not have another top-50 player. Maxing out Walker would cramp their maneuverability in finding one. Walker will be 29 this summer. He's short -- a defensive liability in the wrong postseason matchup. Paying a top-20 player into his 30s as if he were a top-eight player can hamstring a franchise for years.
Charlotte can't tank with Walker on the roster. They might not be able to contend for anything with him on a max deal. Ironically, that is why Charlotte might throw the full boat at him: Without Walker, what do they have? Without Walker, there is no choice but to tank. Charlotte tanked Walker's rookie season. It didn't work. Small markets rarely have the stomach to tank two and three seasons, at least on purpose.