I think secrecy, desperation, and a sense of tragic impossibility of outside validation of the relationship is the whole reason why slash has so much currency in the first place. Romances between a heterosexual couple of different socio-economic standing/race/religion used to have that, but they don't really any more, at least not where the majority of slashers live. It's what makes a romance a real romance as opposed to a hook-up with financial/procreative consequences.