Because psychic types are OP.
He doesn't tend to use them despite the fact he does not specialize in any one type of Pokemon. Is this just a coincidence or is there a purpose behind this?
He hasn't captured a Steel or Ghost type either and I highly doubt there's a conspiracy behind that. It's just a coincidence imo.
He did have a Haunter for a while.
He never actually captured it; it merely tagged long with him for an episode. Again, he hasn't caught a Steel or Fairy type either. It's a coincidence.
Coincidence. Plain and simple.