9. Why does it matter?
At a very basic level, it's important to point to the immediate causal sources of problems that one wants to remedy, because those sources are the best targets for interventions.
Telling women to cite themselves more frequently is not necessarily going to be a fruitful remedy to a self-citation disparity if men and women with similar numbers of previous publications cite themselves at similar rates, and the disparity is driven by an upstream cause (publication number).