I'm female, approaching my sixth decade, and I lift because my mother had severe osteoporosis. I do not want to be that frail old lady with the walker who breaks an ankle just standing up (yes, that really happened to her).
I've been active all my life, including lifting weights off an on, mostly in winter. It paid off with my first bone density scan at age 50, which showed that my bone density was "normal" - by which they mean  "like an average 30 year old". It has quite likely gone down a bit in the last 9 years, but I lift very heavy weights and am very, very, strong for a woman of any age. Why not? I went to an automotive store last week and bought a car battery. I didn't need any help lifting it into the shopping cart and then into my van. Strength means independence for older women.