A lot of dieting advice and culture doesn't help. Traditionally the objective was to get the number down on the scales and look as lean as possible, usually at a cost of muscle as well as surplus fat.
Added to that, crash diets or low-fat plans like slimming world underestimated how much protein your body needs, making it easier to lose the essential, healthy muscle mass that is metabolically expensive to maintain, especially if not exercising and losing it.
It's only relstively recently that exercice culture has got over its irrational fear of females "bulking" (or their reproductive organs falling out) and diversified away from "feminine" activities like aerobics and yoga into a more equal approach including understanding the massive benefits to the female body from strength work, particularly with heavy weights.
People still cling on to these old, counter-productive, unhealthy beliefs. I still see comments like "don't exercise, it won't help you lose weight" being posted. While exercise can only burn a limited proportion of calories, it boosts your metabolic rate, and especially for women with low TDEEs, a couple of hundred calories a day makes a vital difference between living on a diet that's pretty normal but sensibly managed and what looks like an extremely low, restrictive diet to average+ people.
So many mobility and health problems in old age are caused by sarcopenia (muscle loss). It's a natural process of the body anyway, and worsened in females due to hormonal changes, but that makes it more vital that we have as much muscle mass as possible in younger life, and work at maintaining as much as we can to delay frailty in old age as long as possible.
I have lots of "daft" little goals. One is to keep sitting on and getting up off the floor. When I work with my youth group, I sit on the floor with them, partly because I find it easier communicating on their level, but also it's a habit and motion that I don't want to lose. It's a major functional strength issue, and it's common for older people to fall (contributed to by weakness) then be stuck for a prolonged period causing health issues, rather than specifically the fall injury being the major issue.
And besides all this decades-away active living, muscular shapes look healthy and good in youth. 