The popular notion is that an only child is produced so that their parents can shower that child with all the resources and attention available. I have another theory. The reason many only children exist is because they were pure accidents. When I say pure I mean a male and female had no intentions in the present or the future to have offspring together. Think 1 night stands and young couples.
This is how it goes. A man and woman have sex and as a result a kid is involuntarily produced. Chances are they are poor and don’t love each other that much or at all. In a situation like this, having a second child is more than out of the question which creates an only child. Often the unexpected child was such a burden that a decent opportunity to have another child never presented itself.
Quite often the parents get married to try to make the whole family thing work but it usually ends up in divorce. They try to hold it together for at least until the late teenage years of their child but sometimes it doesn’t even make it that far. They say only children are attention whores and spoiled. Maybe they’re attention whores but it’s hard to be spoiled when your parents are poor. Think of an only child and ask if their parents are still together. I think most likely not.
The only child is not that common in my experience. Everyone might know a couple but out of all the people you know how many are only children? In my life it’s about 5% or less.
I don’t know if I can say anything else about being an only child besides it’s quite often because of accidental means. I’m sure there’s other things I’m not aware of. One funny thing in elementary school, there were 3 of us who were only children and we all had the same first name. One ended up being an accessory to murder and the other almost killed himself in a car accident and had a whore take all of his settlement money.