With the Monkees' restored HD Blu Ray box set and new album, Good Times, about to be released on this 50th anniversary year, I thought I would offer this perspective.
First a disclaimer. This is not a thoroughly researched doctor's thesis. My doctor can research his own thesis. This is just my perspective from when I was growing up when the Monkees TV series was a staple of UHF stations, and their Greatest Hits album was in every neighborhood kid's record collection.
What I seem to recall is that us guys seemed to be bigger Monkees fans, while the girls seemed to prefer the Beatles. The obvious reason for this could be the TV series. Much like The Three Stooges, which is considered "a guy thing" that girls never got, the Monkees TV series, with it's fast paced comedy, drew the guys in while the girls shrugged at the whole notion. But I think it went deeper than that.
The Monkees, on the other hand, had the majority of their songs aimed to a guy's life experiences. In the Monkees' music continuity, girls were not the objects of happiness and romance to be adored and put on a pedestal like in the Beatles' world. In the Monkees' world, girls were most often backstabbing heart-breakers ("She", "Mary Mary", "Stepping Stone", "Tomorrow's Gonna Be Another Day", "Gonna Buy Me A Dog", among others), people not to be trusted ("The Girl I Knew Somewhere", "You Told Me", "Forget That Girl", "Cuddly Toy", "Words", among others), and selfish users ("Star Collector", "She Hangs Out").
While in the Beatles' world, the goal was to hold hands and have a relationship, in the Monkees' world, the goal was to be friends with benefits ("I Wanna Be Free").
I was listening to "Sunny Girlfriend", thinking it was a typical teenage love song. The whole song is about saying how great this girl is. But then the final line reveals the truth- no matter how wonderful you think this girl is, and how much you're in love with her, "she doesn't really care". That kind of songwriting speaks to pre-teen and teenage guys.
Even in the Monkees' more traditional and optimistic love songs, the guy seems to be falling in love against his will, if you really listen to "I'm A Believer" and "Love Is Only Sleeping" and "Look Out Here Comes Tomorrow" and "What Am I Doing Hanging 'Round".
So, my unscientific conclusion as to why, when I was growing up in my Midwest neighborhood, the guys were Monkees fans while the girls were Beatles fans, is that the Beatles tailored their songs to girls, and the Monkees tailored their songs to boys. Just don't ask me why then Monkees concerts are loaded with girls in the audience. But then, why should I speak, since I know nothing?