Well, simply put, there called legendaries for a reason. Game freak makes these Pokemon hard to get so that they are rare. I mean, could you imagine trying to have a legitimate battle against a guy with 6 arceus? Not to mention that a lot of legendaries are pretty much gods in the pokeworld, so it kinda takes the magic out of it when some kid has six gods of time and a PC box full of the original creator of the universe.in addition by making these legendaries rare and hard to get, trainers can use their non-legendary pokes without them being obliterated by the god of the sky. Also, having easy access to legendaries would make the game too easy to beat and somewhat ruin the gameplay experience.to add on, events are intended to be rewards for dedicated players, as is catching a legendary. To sum up, legendaries are hard to get so that you can only have so many and so that you have to raise normal Pokemon to beat the game, enhancing the gameplay experience.