When I feel close to a man, I just feel close to him. When I feel close to a woman, I want to have sex with her. Why?

I'm a man, I get to share ideas and feelings with many different people of both sexes, and one feels close to some. Although I believe in theory when psychologists say we're all bisexual, I find that when I feel close to a man I don't have that strong sexual attraction like with a woman. Why?

I tend to think that no matter how close two guys are, they always feel a little competitive with one another, which takes some joy out of homosexual sex. Is it perhaps the same with two women? Whereas I don't feel so competitive with someone of the opposite sex. But not sure this is really the explanation.