There is some overlap though. I tend to find (certainly on en-wikip) there are some articles which could be explained in layman's terms, particularly in maths and physics, that don't bother and just launch into a forest of LaTeX.
I agree that every article ideally should have a "Subject in a nutshell" explanation in the introduction (which again brings us to the problem of the participation of academics). But it does not mean this explanation can be always made available for 10-years olds.
Cheers Yaroslav