I am aware of it but no idea why specifically.

Maybe vtubers feel more real than normal women YouTubers cause if the visual is fictional than the personality being fictional fits making a fictional character so that there isn't a dicotomy between real visuals and fictional personality ?

While men tend to be a bit more genuine so it doesn't quite work if they try to vtube as well since it again mismatches ?

Just spit balling here as I have no specific idea on why.