As population increases, animal souls are promoted to human before they are spiritually advanced enough in terms of impulse control, etc.: this shouldn't have happened, but karmic progression is automatic, after all--it's a force of nature. But the 'animalization' of humankind bodes ill for civilization.
No doubt the same goes for elves, dwarves, and so on.
There is a land where every person wears spectacles. Those without eyeglasses are considered to be the lowest stratum of society, so adventurers without glasses are treated like outcastes. It certainly would explain those heroes wearing sunglasses for no apparent reason...