Day and night are designations that the game itself can have
The cards soft colors and charming design make it a fan favorite
The calamity of Sin is endless and the cycle keeps repeating, because when Sin is defeated by the summoner, the summoners guardian becomes the new Sin
Outside of my favorite franchises dinosaurs, there are other prehistoric creatures galore along with distinct takes on the fantasy classics like ancient vampires, undead pirates, and a menagerie of other beasts and beings
So while a token with undying still triggers undying, it wont be in the graveyard to return to the battlefield when the trigger goes onto the stack to resolve
Because of that, I think Konami doesnt feel like they have any real reason to want to bother releasing them