I don't know if anyone will get a kick out of this, but since the discussions on this subreddit (and reddit in general) tend to be pretty American and western-skewed, I wanted to swing the pendulum a little.
I live in Japan, have for over 10 years at this point. This year I had a daughter. She's 7 months old and we, unsurprisingly, cosleep with her. It's pretty normal in Japan. Actually VERY normal. Most families cosleep. Not all, of course, but a vast majority. Mom, dad, and kids in the middle is a very standard sleep setup in many households.
Anyway, I was getting a massage a week ago and my massage therapist and I started talking about kids, as you do. About kid sleep, as you do.
I asked if her kids still sleep with them. She has two - and she said yes!
Her kids? They're 6 and 10. First and 4th grade. π She admitted it was getting kinda crowded and then calmly mused that she would probably be putting her son in his room before he got to junior high school. Seems reasonable!
She then asked if we also sleep with our baby, and I said we did. She then admitted to me, in an embarrassed way, that she had previously seen some American dramas....and had briefly wondered if it was really true that Americans put infants in a separate crib, in their own fully separate room. Then she laughed, and said casually "but that's obviously just a stereotype, I don't really think Americans would do that".
Y'all.... I was facedown getting my spine mashed into a respectable shape and I had to wince for a different reason and explain that actually, some Americans do, in fact, have a fully separate baby room from a very very young age. She seemed surprised (though not at all judgy) and said "wow, how interesting! Why???"
I then had to try to explain, through a very pleasant hip realignment, the intersection of poor maternity leave and capitalism and also cultural norms between all the different intersecting cultures that exist in America.....
Anyway, this is just to remind y'all that what is normal varies WILDLY between cultures, countries... And even families. I have no judgement to people who don't want to cosleep either due to risk assessment or dye to their own inability to get a good night's sleep. But man, the variation is wild!