benefits could be a material benefits: for example someone try to be close to you ,just for wealth
or power or ....to use you for his own affairs ,.... and go one .As it could be moral or psycholgic
benefits ,which explain why lot of men aren't looking for frindship with men ( i deduce that you
fell in this problem and it's your motive to ask this question :-) ), and vice versa for women , i think that such behaviour is related to many factors, for example the lack of care ,because every humain being likes to find someone who cares about him,listens to him ,and when he asks him ( how are you ? ) he listens to his answer carefuly , and as males and females have an inborn attraction to each other that makes it easier to find one with this caracteristics from the different sex, and in some ( if it's not the most ) of the cases men search for desire and women search for love ,in such realtion ships the interests are huge , As a result the relation between people of the same sex is affected by the previous factors, ( don't forget the accusation of homosexuality for such frienships in some cultures ) ....