In my opinion, separating romantic and sexual attraction has been embraced because it stabilizes opposite-sex relationships while destabilizing same-sex relationships. A "heteroromantic" bisexual will always be using gay men or lesbians (depending on their sex) for sex while only engaging in opposite sex relationships. Our intimacies will always be fair-weather and fleeting and queer theory ideologies hope to keep it that way.

You can see this trend with the bodies pushed on gay men and lesbian women. Either transgender bodies, which are the opposite sex so we engage in heterosexuality, or asexual bodies, so we can be in a same-sex relationship but without the sex. IMO, it's also why open relationships are pushed so hard on gay men- they destabilize our relationships and promote the idea that we shouldn't work on being better for our partners, that we should keep a relationship going even if we don't want to be with that person (because breaking up is 'problematic'), and that you can't expect sexual exclusivity from someone you're committed to.