I think it's proof that people really like the camera, or the battery life, or the calculator app, or etc. Without actually asking people, how are sales number

I think it's proof that people really like the camera, or the battery life, or the calculator app, or etc. Without actually asking people, how are sales numbers proof that buyers care a lot about any specific aspect of the product? And why is everyone forgetting that obviously Apple does ask people and run focus groups, they know very well what their customers are most interested in.