I have to assume a huge amount of it is national and local regulations, which seem to change every freakin year. I read relevant sections a decade ago re: outlets with no ground(has to be on gfci breaker) and wiring a bathroom(has to be on separate circuit). Now you're apparently not allowed to put outlets on the side of or back of kitchen islands? Just random things like this.

I couldn't imagine having to keep up with all of it. I'd guess many don't...