I think people confuse what alphas and betas really are. It actually comes from wold packs and social hierarchy within them. The alpha male is the leader bc he is the strongest male in the group, and mates with all the desirable females in the pack. The other wolves have sex with the less desirable wolves sometimes but it is rare bc in the animal kingdom less desirable females are older and usually die off. There are also the rtypes, like the sigma wolf who is not part of the pack..a loner who sometimes mange to have a fling and mate with one of the packs females. Throughout most of human evolution we lived that way. Recently we started pair bonding where men and women would pair off and mate together, usually for about 4 years until the child was old enough to not need direct care from the from the mother and protection from the father. then they would break off and paint with other people and mate again.
Most of the people I see who claim to be alpha males are not leaders and fairly low on the social heirarchy. Also human socialization has become far complex with specialization and trade that a person can have many different roles in different areas of his life. A bodybuilder might be the leader at his gym bc he is the strongest in that area, but be very low on the social hierarchy so in other areas ofd his life is not the leader or does not have much power over others at all. A successful banker may have leadership position at his bank and give orders to his inferiors at work but when he leaves the office is seen as a lower class rich guy and cannot attract the most desirable upper social class he women he wants. I dont know the movie you are talking about bc you didn't name it. I think that in most genres of film though, when there is a hero that character bus a leader bc that is what is required. Also low social class people who lack leadership abilities are not able to rise in society on a fair playing field. They usually have to break the rules, trick people, or do immoral things like lie to women in order to have sex with them.