Why do some gays and couples try to mimick a heteroual relationship?

Why do some couples ume the roles of 'butch and *****' or the 'lipstick lez and the butch lez'? I don't understand it. Why not just be the gender you are. Females are naturally feminine, men naturally masculine. I undertand that sometimes men are naturally more feminine in nature, or women sometimes more masculine in mentality. But why purposefully go out of your way to mimmick the opposite gender? Why do some s feel the need to get short haircuts and wear crappy baggy clothes? Why do some men feel the need to dress like women? Why not just be ual but embrace the gender you were born as?