No it's not working/SAHPs or middle class/working class or older/younger parents or even SMOGs vs the rest of us.
It's those with an only or youngest in R/KS1 and those with a hanger on toddler or preschooler!
I'm in the latter category and we've lost all DS preschool friends as they all went to different schools, so we're trying to do playdates.
But I find it really hard to have 2 excited 6 year olds plus a whiny 3 year old who is too young for their games. So I keep having to say "not that day... No not then either as I'll have DD". I owe 3 or 4 now I think. Plus activities - trying to keep DD occupied during DS lesson.
Also those that work part time but have no younger ones or a portable baby are always heading off for a grown-up coffee after drop off, while I have Miss Fidgetybottom who doesn't want to be dragged to grown-up places.