Adolescent girls may spend a significant amount of time in the bathroom due to reasons such as privacy for personal care, exploration and experimentation with appearance, socializing, concerns about body image and self-esteem, establishing hygiene habits, seeking escape or solitude, and addressing health and hygiene concerns. Understanding these factors with empathy is crucial for supporting adolescents during this developmental stage.
Grown women also spend hours on enhancing their looks and buying clothes that display their bodies. This is more than a development stage. It is a passive sexual behaviour that women (and some gay men) use to attract men. Adolescent boys spend time in the bathroom to get the privacy for masturbation. This is the contrast of the sexes where the male focuses on his own sexual response and the female focuses on attracting male attention. Both of these go in the same direction - facilitating reproduction through the male response. Nothing to do with female responsiveness.