Why accurately measure incident light in studio photography?

I wanted to understand the value of incident light meters and tried web search for “Why measure incident light in studio photography?”. I found into that such meters measure light more accurately. I understand the logic, I know accurate color representation is important to show objects on photo as they are in real life. But in studio total light exposure is what is variable (not “natural”) and depends on powers of light sources and amount of light is just one number (lux), no need to measure complex relationships like for RGB correctness.

What is the point of correctly measuring amount of incident artificial light? IMHO it is the amount of reflected light that defines how photo would look like.