Open relationships in the gay community?

Lately I've notice alot of male couples in the gay community are having open relationships (as in having sex with a third person or other couples). I want to know if I'm the only one that has an issue with the whole open relationship thiong because alot of people in the gay community is ok with it.Not saying that it's not appening in the heterosexual community, but it seem as if I mostly here about it in the gay community. How can someone be in a commited trusted relationship and want to have sex with other people besides their partner?