Half the threads on Mumsnet are filled with people surprised that things are different in different circles.
If you live in a suburb where every school has a small catchment and there’s a pavement everywhere you want to walk, then it makes more sense for older children to get to friends’ houses independently. In a rural area, with pavement-less roads and long distances, not so much. Children going to independent schools are also likely to come from a much wider area. As with anything else, it all depends.
I do sometimes stay and chat when my child visits friends - because the other mums are my close friends. We’d be organising a coffee at some other time anyway, why not do both at the same time?
I think the issue here is the siblings, as I can see that three DC plus an adult must feel like too much, especially when you have a small baby.
Sleepovers: not related to the OP but in general, no one is obliged to explain why they don’t want their children to take part in sleepovers. It’s a personal choice and completely up to them.
I personally find it a bit bizarre that parents go to huge lengths to protect their children from strangers, but are quite happy for their children to be bedding down for the night easily accessible to men that they only really know as ‘Lucy’s dad’ or ‘Angela’s husband’.
Read any thread on here about CSA if you’re in doubt. Hopefully it never happens, but why add that risk?
There are also medical reasons why sleepovers might not be ideal. Epilepsy, diabetes, allergies, bed wetting, sleep apnea, night-terrors…none of this is anyone else’s business but the child and their parents.
So if someone declines a sleepover then, rather than taking it as an affront or assuming that parent is controlling, perhaps the kind thing to do is to accept it without questioning and try to include the child or young person in other ways.