NO POKEMON BANK FUNCTIONALITY
Pokemon Bank was a incredibly useful 3DS app that Game Freak made a while back, that essentially allowed players to collect and collate all their Pokemon across various Pokemon games in the app. So if, for instance, you had Pokemon from X/Y, and Sun/Moon in your bank, and started playing OmegaRuby/AlphaSapphire, you could transfer all the Pokemon in your bank over to them. Additionally, if you had a ton of Pokemon in your ‘Dex in any save but wanted to start a new save in that game, you could always send your Pokemon to the bank and then restart the game without worrying about losing your Pokemon. Pokemon Bank functionality isn’t enabled in Let’s Go, which is at least somewhat understandable, since it is, after all, a 3DS app.
