Because Pokemon has a sense of a foreboding apocalypse.
Well, Cyrus did try t' literally destroy every ****in' universe and beyond in an attempt to create a new world.
i haz 1337ƒ lawl
In all honesty, I believe that whole srsly srs vibe towards Gen 1 has come about from over-speculation. RBY is definitely the least kid-friendly of the games, but ya have t' look damn hard to see said kid-unfriendly junk for what it really is.