In Freud’s theory, masochism is from sadism, another theory said that sadism and masochism are two faces of one coin.
But the recent study shows that maybe masochism is more fundamental. The number of Masochists are much more than sadists’.
The submissive partners are really in control during SM, because it is the submissive’s desire shapes the sex play.
Masochistic desires are much stronger than sadistic. But many submissive people cannot find a partner to dominate them because of the shortage. So What happens often is two masochists meet each other, one of them should take turns.
Many dominant have the submissive experience, maybe masochism is more important.