“ Historicly, we have had plenty of rl groups like the Taliban and the Puritans who supressed anything which was in any way fun. What if there was some group that was the opposite? (which in time would cause problems of it's own for the civilians under their control.)”
“ A certain patch of forest is well known for causing anyone who ventures into it to suddenly go blind. Once they leave the area their vision returns. Rumors of treasure hidden within.”
“ When you sleep, your soul briefly returns to the place where it was created/goes to when it dies, and seeks nourishment. Everybody's soul is created with a little link (or you could say a greater entity calls it back) to that place so that it can return easily, but upon death, the soul returns via that and annihilates the link as if returns.
Also, as an added thingy, you could say the entity supplying the link, or residue of the links themselves, (whichever) is the source of all arcane power.”