>>12093029It's possible that, because he first 151 Pokemon had Slowpoke, Slowbro, and Starmie as Water/Psychic type already, GameFreak didn't want to add yet another Water/Psychic type.
Though, it would make more sense for Psyduck's line to be part Psychic-type because of the repetitive notion that it constantly has headaches and releases tension during its worst headaches by unleashing psychic powers.
It's perplexing to try to understand why a Pokemon named PSYduck isn't part Psychic-type.
