They already do.
Matter defines a minimal common language. Manufacturers must expose basic features that exist in the spec. Thermostat: Mode, Setpoint, Fan. Locks: Lock/Unlock, PIN management. Lighting: on/off, brightness, color. Philips Hue: Gradient control and power-on behavior are all hub only. Aqara FP2 exposes only occupation. Zones, room mapping, sensitivity and multi-person tracking requires their hub.
Anything outside that, including OTA in many cases, requires the manufacturer’s hub.