Clarified butter is butter from which the water has been removed. However, when making clarified butter, the butter is heated more gently, just enough for the oil and water to be separated. The water phase contains all the proteins and sugars. So once the water has been removed, the initiators of the Maillard reaction are gone. Even though fatty acids can join some of the reactions in the Maillard reaction 'party', they can't initiate it themselves and will be stable under high(er) heat.