Yeah, and many are easily identifiable with something weird like “.com” in the OT’s name. While shiny 6-IV Pokémon aren’t impossible, it’s immensely unlikely to find someone willing to trade one to you via wonder trade or GTS.
And for Pokémon from some of the games, especially the older ones, there are programs that determine whether a Pokémon was hacked in or not due to the unique way a pokemon’s Rng interacts with a trainer’s SID and TID values, depending on encounter method. :P