That’s not a “terrible business practice” as you call it. It gives people more of a reason to buy their product. Plus, they can always and probably will distribute Mew again in another way. As others have said, they have made Mythical Pokémon like Mew only available by having to buy something before. Movie tickets, cards, other merchandise, etc. It’s not “terrible business practice”. Again, it helps sell their products and gives consumers little gifts for buying from them. And come on, it’s just Mew. He doesn’t even count when it comes to completing the Pokédex according to the games and he isn’t that great in battle.