Why no 'Hidden' junction boxes?
In part, the reason for building codes is to hold contractors to a certain minimum safety standard.
So I can easily understand building codes like GFCI outlets for wet locations (kitchen & bath).
But what is the reasoning for the code that basically states that all junction boxes must be accessible?
I just don't see the "safety" factor in such a code. The splice doesn't know that it's hidden, and the wire is more protected in a box than just running inside the wall. So the code isn't written as a means of preventing a fire (like codes that specify minimum wire sizes do). Wire in the wall is stapled so it can't go anywhere, so there isn't any advantage from a stand point of being able to pull the wire out later.
Now I can guess as some reasons, such as being able to maintenance the junction in the future to check for corrosion or something like that. But nobody "maintenances" electrical wire (except for when something has gone wrong). So given that you could put a note on exposed wire indicating there is a hidden junction box (in case that needed to be known in the future for trouble shooting) why isn't that allowed? (i.e. to the best of my knowledge, there isn't an exception to "no hidden junction boxes" "if you do X").
Just because a junction box is hidden behind a wall isn't going to make it more likely that
Through sources like this forum, I've learned that it is against code to have a junction box that is hidden (i.e. sealed up behind a wall).