Hi Taz,
The way I see it is down to luck.
Like any other disease, you either get it or you don't. I'm not going to go into the mental trauma of telling myself 'if I don't go on HRT, I will get osteoporisis' because it's purely a speculation. I cannot allow myself to think that a lack of oestrogen and not taking HRT are the culprit of any disease I might get in the future. I associate diseases with age. For men, I've never heard that a lack of testosterone will cause them to have a heart attack. They, like us, get old and are prone to diseases but nobody has ever said that it was hormone-related.
Going back to osteoporosis, I know a bunch of long-post menopausal ladies who haven't got osteoporosis. A few ladies might get it but not all of us will.