How come girls obsess over boy bands?Watch
Most boybands are only "famous" because they look like little Ken dolls, not that they have any singing talent.
Just realised while I'm writing this that most boy band songs often use direct pronouns, like "you". I guess that adds to the pseudo-relationship between the bands and their fans.
Then again what do I know?
I don't understand the obsession either but not to sound arrogant and to answer your question. According to psychology the Absorption-addiction model argues those who pursue parasocial relationships (celebrity worshipping, staking etc.) do so due to deficits or lacks within their real life and these relationships are seen as an attempt to cope with or escape from reality.
My guess is that it's kind of considered the social norm nowerdays for girls to like boy bands. If their friends claim to adore a band, then to fit in, they'll learn to love them to.