Having purchased a used Evader ST and a hopped-up completed RC18T factory team, I have to say there is no way I would have gotten into the hobby if I had started out with pieces.
I'm learning how things work when they break, both by trying to figure it out based on the manual PDFs online and by asking when I don't understand.
I think that on both sides of this there is a missing demographic - those who learn by taking apart, and who learn by recognizing the differences between broken and not.
I am one of those people, and my father is as well. He has sailed his hand-built custom-designed RC sailboat (based on a boat he sailed for years in person), for a long time, recently it was as much as daily.
We inspect every millimeter when things break. we identify the problem, and may ask when we cannot rectify the problem without a specific part.
Please don't put this demographic out of the way in this discussion. We learn by observation, and when our observation does not come to a complete conclusion, we might chat up our LHS for other advice - and we remember it all.
I would never have gone anywhere near RC if it required several hours and several hundred additional bones for my first car, but that does not mean I wouldn't take it apart completely.
Don't underestimate us!