For professional drone pilots that kind of flying would be a piece of cake. Then the fixed-wing becomes a bi-directional relay for the drone control. The motorcycles seem to crash or cause crashes every year...
And still, moto/cyclist crashes happen and replacing them with drone/cyclist would be worse.
The motorcycles are an eyesore, they interfere with the race, and they emit noxious gasses for the athletes to breathe. Replacing them with drones seems like the thing to do.