There are different ways of looking at sexual motivation.
It can be viewed as a mental entity, which can be manipulated for pleasure. As far as pleasure is concerned the nature of the parties involved doesn't really have any significance. Of course, there can be other considerations, such as the exploitation of children, seniors, celebrities, animals, plants, the ground, monuments, historically-significant artefacts, Extra-terrestrial naturalists, and/or significant sections of continental coastlines and/or airspace. But the pleasure itself is dependant solely upon satisfying the individual.
There are also social elements. Depending upon the traits that are considered effeminate or masculine, sexual activity can associate people with various traits and social positions. Now societies often involve a great many different relationships between a great many individuals and groups and are largely dependant upon the nature of the entities involved. So it isn't really practical to make generalisations, so all I can really say is that it could have a significant social effect, depending upon the societies it takes place in.
For example, a society that regards one gender as dominant, may regard activity between those who share that gender as an extension of this, garnering them even greater respect.
Alternatively, a society that values lineage may regard such activity as a failure to perpetuate the lineage, and therefore a failure to the community.
It can also be viewed as a biological imperative to perpetuate the species. An imperative that does not exclusively perpetuate the species is wasteful. An imperative that fails to perpetuate the species is a disability. The evolutionary implications are obvious...