Often expressed subtly, heterosexuality is widely "accepted" as the default sexuality by both print and electronic media, education, law makers, and a range of attitudes expressed by society in general.
The subtle assumption of heterosexuality can be very harmful to those who do not entirely fit within its bounds.
A Heteronormative assumption that a girl will grow up and marry a man.
Heteronormative children's books only portraying heterosexuality.
Heteronormative TV Shows only portraying heterosexuality and the assumption that every character is heterosexual.