It adds depth to the character. Imagine someone of that sexuality in a situation like this. The fear of not being accepted and possibility tossed out in the street to die. Its hard enough for anyone homosexual to have the common rights and freedoms in society now. Imagine what it would be like in a society devastating like this one is. Its going to be expected that the limited number of females pair up with males to at the very least continue the species or at the most to relieve the need of human sexual desire. Someone of a homosexual sexual orientation isn't going to want to have much of that form of contact with a heterosexually oriented person.