They’re not ALL defective. I used to be one of them, so I guess some are. But I know some who aren’t.
But, we clearly need to acknowledge that some boys and some girls are defective and there are reasons they won’t get married for a while until they work some stuff out, or maybe until they find someone who can work for them, or maybe never.
I personally think there are more boys than girls who are like that. I call it the creepy guy theory of the shidduch crisis.