I think there can be a big difference at different moments in a family's HE journey.
A family who have known they will HE from the start can have a really organic, gradually evolving social life which segues from the ordinary pre-school-y stuff into whatever it segues into - I'd say that 5/6th of the families we see regularly are NOT HEers.
But I think that a family coming out of school, particularly in traumatic circumstances, and particularly if they don't already know any HEers, can be really reassured by meeting a community of other people who are transgressive in this particular way. I have spent quite a lot of time at HE meet ups saying (a la sybil fawlty) "oh I know" and "oh, poor things" as a mother details the horror of her child's school experience - and it's much harder to have that conversation with people who still believe that, given the right nudges, school could have Got It Right.
I almost think some families need to find local HEers as part of the process of finding their feet in thenew lifestyle, which might not in the end involve many other HEers at all. Or it might. whatever.
On another note: I am not really up for detailing my children's social interactions, partly because, for me, it is too invasive of their privacy, but also because it will never reassure someone who is anxious about my children "missing out" on the schooled socialising experience. I could detail daily educational organised classes with other HE families, where the parents leave the children there and there are clear rules about interacting within the class environment, and set play times (i.e. as close as can be to school without being called one) and the doubter would still find something to be anxious about. NB I invented that school-esque situation for rhetorical effect...
The fact is, HE is societally transgressive. "What about socialisation" isn't actually about whether you can make enough opportunities for your child to play or work with other children (what's "enough" anyway?), or to interact with other people without parents in the background oops here's mr tesct... gtg