Despite its popularity, why is Melmetal not in Pokémon Scarlet and Violet?

I knew that Melmetal was a popular Pokémon among most fans. However, unfortunately, despite its popularity, it was not made available as in Pokémon Scarlet and Violet, not even in The Hidden Treasure of Area Zero, Pts. 1 & 2: The Teal Mask and The Indigo Disk. So, by the way, I'm just wanting to know why you think that Melmetal is not in Pokémon Scarlet and Violet, not even in The Hidden Treasure of Area Zero either despite its popularity? Please let me know, thanks.😉