But many times you want to be clear you're referring to that sex, irrespective of age. So using "woman" isn't any shorter -- writers inevitably end up using clumsy constructions like "women and girls"[1]. We have a word for the union of the sets. Just use it already!
I'd be glad to entertain it as being dehumanizing if we had a less-dehumanizing, shorter term for the same semantic space. But as there isn't...
Similar issue for "male" and "female" as adjectives; to my ear, "woman doctor" and (especially) "man doctor" sound a lot clumsier than "male/female doctor".
[1] From a quick Google search, see the CDC and a big pharma comapny:
"Which girls/women should receive HPV vaccination? HPV vaccination is recommended for 11 and 12 year-old girls. It is also recommended for girls and women age 13 through 26 years of age...". (Emphasis added.) Lovely! http://www.cdc.gov/std/hpv/stdfact-hpv-vaccine-young-women.h...
"GARDASIL®9 ... helps protect girls and women ages 9 to 26..." https://www.gardasil9.com/