How do people with Autism end up in relationships with other people?

I read a lot and I know people who have massive psychological issues, yet they have sexual relationships or a husband or partner. I don't get it. They are often deeply unhappy and damaged, they feel worthless, have autism/ADHD, but they have found someone who likes them enough to be in a relationship with them. 

Basically its confusing for me because I have never been in a relationship, I have autism, have spent 10 years totally rebuilding my psychic/mental health, yet I haven't come close to being in a relationship with anyone. 

Thanks.