Theory time - it could be due to reduced natural Vitamin D from lower sun exposure, a mostly sedentary life, combined with less life long physical labor (especially for women, who are severely under-represented in construction and heavy industry, which is about the only places you'd get that kind of exercise in modern society).
Lifting weight helps bones get stronger, and Vitamin D is an essential nutrient in proper bone building.
100 years ago even, most people lived and worked on farms in the US (and many other places), now it's single digit percentages - and many of them spend it driving vehicles and similar less physical labor.
Because women have dramatically higher fracture rates due to osteoporosis (and lower bone mineral density in general) [https://pubmed.ncbi.nlm.nih.gov/11063899/], the only known way (outside of some, last I heard, unproven clinical vibration treatments) to get stronger bones is to lift heavy things while having proper nutrition, and about the only occupational exposure you're going to get to lifting heavy things on a regular basis is those industries?
There is also a similar visible skew in the power lifting, olympic lifting, or weight lifting communities for those into it recreationally.
It used to be we all spent more time lifting heavy things. However, post WW2 that has rapidly declined.
So one way to reduce or reverse this is if we ALL lifted heavy things more often. From a risk reduction perspective, that seems to be especially valuable for women?
> So one way to reduce or reverse this is if we ALL lifted heavy things more often. From a risk reduction perspective, that seems to be especially valuable for women?
Depends; women might be much more prone to injury from lifting heavy things.
A lot of women I’ve lifted with were proportionately stronger than most men I’ve lifted with, injured less often, and more capable of lifting heavy things than I was. The person who taught me to deadlift was a ~140lb woman who could pull 330lb off the floor with her baby strapped to her. She was exceptional, but anecdotally I’d say women can lift whatever they want without any added risk of injury over male counterparts.
You're seeing the statistical problem of "restriction of range". Weightlifting women are one of the worst possible classes to try to generalize weightlifting ability from.
Lifting weight helps bones get stronger, and Vitamin D is an essential nutrient in proper bone building.
100 years ago even, most people lived and worked on farms in the US (and many other places), now it's single digit percentages - and many of them spend it driving vehicles and similar less physical labor.