Okay, seriously, I do not want to get into an argument about this, but there are a couple of points I feel need to be made:
My GP is a former paediatrician and has been working for many decades, in her opinion there is no benefit in taking calcium or other supplements if diet is adequate
You've said it yourself, and I can tell you from my own experience as a breastfeeding mother whose calcium needs are triple what they used to be and who suddenly had her diet severely restricted from its previous range that my diet is
not adequate and I require supplementation.
I am against supplementation for supplementation's sake, but sudden dietary upheaval on a background of increased need anyway is very good indication for supplementation.
It's a an undeniable fact that in countries with lower dietary calcium intakes and where calcium supplements are unheard of that rates of osteoporosis are far lower.
That is not a fact that is backed up by the International Osteoporosis Foundation.
https://www.iofbonehealth.org/epidemiology
If a fact is undeniable then you need to quote sources so that I can critically evaluate the paper. As it is, I'd hypothesise that low rates of osteoporosis in other countries ("countries" being non-specific, because there's a big difference between, for instance, The Netherlands and Papua New Guinea) would be because of low diagnosis rates rather than because of low disease rates. Basically, if you don't go looking for it, you won't find it.
And since the gold standard way to diagnose osteoporosis is via radioisotope bone scanning, using a fancy piece of expensive equipment that many countries can't afford, I'd guess that most places couldn't go looking for it even if they wanted to. Osteoporosis can not be diagnosed by X-ray. It's a developed nation disease because the developed nations can afford to diagnose and treat it.