We do though sometimes. With kids. It's easier for kids to understand "this is a boy/man or girl/woman animal" rather then scientific terms like male and female. Though could be different in different languages...

[–] bellatrixbells [OP] BoobatrixRex 0 points

I do wonder for other languages. In French we will say things like "this is a female cat, which means it's a girl cat" or something of the sort. That's how one acquires the basic concept that sex isn't unique to humans.