I live in Amsterdam and I am gay, so I know what I am talking about. ;-)
The *vast* majority of visitors to the Gay Pride Parade (locally known as the Canal Parade) are heterosexual ladies. Where else can they see thousands of bare-chested good-looking men for free? Last year I heard one of the girls comment to her friend: "Wow, can I be a gay man, too? They are all so cute!"
And the street parties, open-air concerts and open-air movies are good too! Gays just have more fun! ;-)