I think the majority of people who draw/paint/render humans tend to use models who are in their age range (by which I mean, child, teenager, young adult, adult, or elder - to borrow life stages from the Sims!)

I remember drawing kids when I was a kid, and my little boy draws children, but the only adults he draws (and the only ones I drew) are people he knows (me, his Dad, etc) or "fan art" like Doctor Who. 

This tendency to not use the kids is then reinforced by their not having much clothing/textures available - a bit of a vicious circle.

Aside from the toon/fairy stuff, when I see an image here using a child figure, it's very often used in some sort of "social commentary" situation - a child begging, or sleeping rough; a child in fear of an adult; being bullied or excluded; etc. Often I see artists producing this kind of work as a catharsis for their own childhood pain (or that of loved ones), or to "speak out" on a particular issue.

Speaking for myself, I produce that kind of work so rarely that I won't buy clothing for the kids because I can't justify spending money on something I'll only use once, if ever.

Notice how drifterlee said she was making a cute kid pic - for her daughter? She has 674 images in her gallery but until now she never realised how small the market for kid stuff is :-)

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"you are terrifying
and strange and beautiful
something not everyone knows how to love." - Warsan Shire