'Why do some people have green eyes?' 'Why do some people have darker or lighter skin?' 'Why are some people tall and some short?'
"Guy" and "girl," "man" and "woman" refer to social and gender identities. They aren't contingent on one's physical disposition. I.e. just because someone has a penis (and thus was designated male at birth, DMAB) doesn't mean that that person feels like a boy. Sie might feel that this is a false or incomplete description of hirself. A DMAB person might want to be perceived as a girl in society. Often transgender people describe themselves as "a girl trapped in a male body" or "a boy trapped in a female body." For more information, look up "transgender."
A better way to ask your question might be:
"Why do some people want to experience life from the perspective of another gender?"
The answers are always different. They range from curiosity and creativity through wonder and excitement. Or it may have more to do with what that person identifies within themselves as.
Some people (who are male and identify as men) crossdress (dress up/put makeup on in a way that is commonly seen as feminine) because it's a sexual fetish for them or because they like feeling more feminine sometimes. It is important to distinguish crossdressing for fun from being transgender, which has nothing to do with sexual orientation or practices.
Some guys want girls to make the first move but those are the guys that are cocky and only want to have a lot of girls after them. Guys are more into the chase.
the guys want the girls to notice them
Because girls have babies and guys don't. They need boobies to breast feed. Guys get curious and want some milk too
Some are guys, some are girls.
Well some guys would say guys are, and some girls would say girls are.
Yes, in the beginning of relationship girls like guys who are introvert so that they can listen to what girls are saying carefully but later they want their guy to open up a bit.
Most guys don't understand what girls want. They just do what they think you like. They will try to look tough (which most girls do like.) Yet I find some guys (not often), wouldn't do anything for the girl they like if it means losing their popularity. Some guys, understand what girls REALLY want. Knight in Shining Armour stuff. They take an interest in what the girl has interests in, and trys them. It's usually these guys who will get the girl.
Because they want to be the first one to get in your pants. Some guys are just jerks
Guys views vary but they don't usually want a huge girl, but the don't exactly want a toothpick either, the majority of guys want a girl with some 'details' to her.
they either want to flirt or get there attention
Because they just want you for your money.
Some girls are awesome, and like guys for who they are, some girls like guys cause they're hot, and some jerky girls like guys for their money and their cars.