Ages ago, people had very, very limited dating options: generally only the suitable partners in their village. They didn't have porn to distract them, and they weren't allowed to just stay single because of social pressure and (for women) economic need. It was rare that anyone stayed single, and they were generally considered weird or "unmarriageable".
So basically, people took what they could get, even if it meant someone they didn't care about or worse, someone who was downright abusive.
The higher rate of singledom these days isn't necessarily a bad thing. Centuries ago, these people would have gotten married, had terrible marriages, and produced kids (remember, no contraception back then) that were neglected and abused and grew up to be awful people.
So basically, people took what they could get, even if it meant someone they didn't care about or worse, someone who was downright abusive.
The higher rate of singledom these days isn't necessarily a bad thing. Centuries ago, these people would have gotten married, had terrible marriages, and produced kids (remember, no contraception back then) that were neglected and abused and grew up to be awful people.