@VillageFete i get it. The OP was about no visits being 'the norm', assuming NO health issues and NO bad relationships. I don't think that youre suggesting people should be having visitors in any and all circumstances.
And the bit that you are missing is that in pretty much all the cases on here and in RL I've seen, a poor relationship has been at the back of it. Grandparents, who on the surface may appear lovely, causing an issue whether they are the maternal or paternal grandparents. And in these cases the DH often ends up not being the gatekeeper he should be.
The vast majority of new mums are indeed happy, after an uncomplicated birth, and with nice, non-toxic grandparents, to allow those visits, and do want those visits.
But you are missing one very, very important point here.
Most people who are happy with the visits, have nice grandparents, don't give it another thought. Those new parents, new mums in particular, who have some reason to worry that their first few days will not go as nice and smoothly as they hope, are the ones who are overwhelmingly writing on this site that they need a few days or a week, to recuperate without visitors. Thus you get a disproportionate view.
But still, a new mum should be respected. If she doesn't want visitors, don't start calling her awkward, simply because you made different choices.