Why do girls have a longer time spent in bathroom than boys?  

They have to give longer time for each and every minute detial when it comes to personal hygiene.

wow good question !i think they spend a lot of time as compared to boys.the reason is because of their nature .you know that girls are a little less active in there sports and more active in keeping themself clean.on the other hand boys consider to do better things like hardwork instead of taking tension about their looks!

Anex,
I liked this very much and I had fun going through your post.
Now, I think girls are more cleanliness freak than boys are. They are more into taking care of their body, hygiene and beauty. They have to have lotions applied or hair washed and for those who have long hair it takes up more time.
And sweetie, I love doing lotions and stuffs like that, what about you??

well, women have more things to do to get ready for our day...it takes time to wash our hair,shave, makeup,lotion,everything. Boys, and men, are more simple just shower and go basically.

Yes, girls are considered to be more detailed and guys are just doing it as a routine, showering only to get the comfortable feeling, guys have enough confidence even if they are not that perfectly clean. People tend to be detailed too when dealing with girl's performance, her skin ( any acne ? ), armpit ( hair or pigmented area ), legs ( smooth or hairy ), and so on... It does make sense that girls have to be extra carefully to get the positive image. Fortunately, hairy armpit and hairy legs are male's treasure that we ( I am a man ) are very proud of :p