Legendary Pokémon can’t be left to defend Gyms in Pokémon GO

The millions of Pokémon GO players out there will soon be able to discover and battle Legendary Pokémon. In addition, if you and your team successfully defeat a Legendary Pokémon Raid Boss, you’ll have a chance to catch a Legendary Pokémon of your own. While Legendary Pokémon will help you take on Raid Bosses and Gym Battles, developer Niantic has confirmed that they can’t be left to defend a Gym – because “they don’t like to leave their Trainer’s side.”

Source: Official Pokémon GO Team