My two cents.
On a more serious note, I do and don't use them. On women's bodies - yes and no. I'm familiar with the overall anatomy however I still use it to put down gesture lines, line of gravity/center, and especially for the head because I work out the overall perspective from 3D shapes and guiding lines with it. I used to not use it for hands and feet, but then I found a very good artist who broke them down in a much better way that actually simplified the bones and muscles (not just making vague hand-esque shapes) and since using his technique my ability to draw hands and feet improved significantly. For anything I don't understand, it's really the only way to break it down and build it up. I might miss the mark using construction vs eyeballing, but at least my construction drawings are a lot tighter and proportional, I find.
I think a lot of people don't use them when starting out because... I don't think most guides are taught very well. They need to actually simplify what's there - the underlying structure and then also demonstrate how these random shapes relate to it. Most methods just teach how to vaguely represent a humanish figure.
