I was going to write a long, in-depth post about how awesome romance options are and how they create even greater depth in already well-developed characters, as well as the greater appeal they appear hold to female players (and, perhaps more recently, with gay/bisexual players as representation improves), but by this point I think I'd just be re-hashing what's already been said.
Instead, I'll explain the
obvious reason why the attractive creatures are not romanceable - they're busy romancing each other.
(Apologies for terrible art - I didn't feel like spending more than ten minutes to make a not all that entertaining joke. Feel free to imagine a male equivalent.)