The truth is, or rather I see it that way, that the game creators just went to satisfy the majority, and the majority of players want to have romansic and sexual relationships at the same time. It's about staticstic. There will be more hetero or homosexual players, who will want to engage their character in sex and romance, than asexual people who won't.
Not saying this is good - but games are limited, it's not RL and game designers have to consider the majority first, I believe. Out of 100 people, it's better to have 70 happy, playing and paying, and 10 who don't care and pay, than 20 who are not happy and cease to pay.