If I go to a car dealer it is because I like to buy a complete car, not a rear end or a set of bumpers. If I am going to build a car myself it will be a completely different story. Then I like to choose which engine I want and the ratio of the rear and also the size and width of the tires and so on. So if I understand you correctly you should just go to the mall and buy a complete ready built robot, this way you don’t have to break down a complex construction into its sections and smaller parts! I guess the shoes didn’t fit after all!
You just proved my point, the point is that you are not going to go to the car dealer and buy the parts you are going to go to the car dealer to buy the whole car.
The whole car represents the robot topic and the engine and elec is the microcontroller and sensors.
So you see that people want a topic just for robotics not just indivual parts.
See what I am saying.