Pokémon belonging to the Undiscovered Egg Group are unable to breed for varying reasons. One of the reasons is for baby Pokémon, which have not yet reached maturity. Another one is to ensure that Legendary and Mythical Pokémon are unique to a single game file masked by the excuse that these Pokémon are one of a kind. This artificial scarcity prevents players from breeding and obtaining more than one Legendary or Mythical Pokémon of any given type in any given game without trading with another game file. It is to note that many Legendary and Mythical Pokémon take inspiration from creatures of different cultures and folklore tales.