I've been wondering this for a while. Like a lot of you, I grew up drawing as a kid. The thing is--and I'm not totally sure my memory's accurate on this--I barely ever drew from imagination. What mostly happened was I'd see something that I thought looked really, really cool, mostly on TV, occasionally in real life, and then I'd be like, "OMG, gotta draw that!" And I'd grab a pencil and paper, try a rendition of it or two, and be like, sweet, I captured it (btw, I've seen a couple drawings from when I was in the single digits, and they were nothing special, but that's beside the point). It was a weird itch I HAD to scratch. Back then, way more than I do now, I found form to be really beautiful, and I was obsessed with cars and robots and junk. I drew the everliving crap out of the Sea Duck from Talespin, because I thought it was gorgeous for whatever reason. I remember trying over and over to draw those giant red and purple robot things from the Xmen cartoon series. I loved Tim Burton's Batmobile, and I remember spending time trying to get it right. I loved the Dragonzord from the original Power Rangers. Gizmoduck from Ducktales. The Enterprise from Star Trek: TNG. Cars I thought were cool. Computers. Video game characters (Samus, Megaman X). Etc.
I think part of wanting to capture an impression of them was that we didn't have a VCR, and I couldn't just record these things I thought were awesome and I wanted to spend time looking at. And there was no Internet, so I couldn't just find shots of them. But I don't think that was the entire reason for wanting to get them down on paper. It was just this really strong urge to do it.
I taught myself guitar when I was a teenager, and I guess I felt some of that same urge to generate stuff I heard that I liked. If I heard a song I really liked, I wanted to learn it and be able to play it myself.
None of this, the drawing or the guitar stuff, was stuff I did because I wanted to show off to other people. I mean, people complimented me and I appreciated it, but the motivation was all internal. I loved to be alone copying things.
As I got older, around high school age, there was shift: I stopped drawing copies of things I liked, and instead I started copying visual styles (anime, or the styles of random illustrators I thought were cool (Yoshitaka Amano, other random Japanese videogame concept people)), but using those styles to draw from my own imagination instead. And the same is true today: if I see something really cool, I don't want to copy it, but I might really want to do something like it. Or if I see an interesting visual style, I might want to try doing something similar, but not exactly like it.
So, anyway, the copying. What's up with that?
BTW, marginally related, I saw this cool timeline of the development of kids' drawing a while ago: