Well...
I can't say I know of an official reason or a law.
Drink? I really don't know why. Law or NH's choice.

For electronics. Is it electronics or just phones that the rule is about?
Personally I believe that the Japanese just took the rule a step further than others. Actually makes sense. Why put this gray area in have to do with when an airplane is on or off the active runway.

In Japan, talking on the phone on trains is considered rude and disturbing to others. Same would go for a plane I'd imagine.

Scho