Shock Wave is a weird move that's widely distributed, especially among Psychic types. All sorts of pokémon get it. Same with Signal Beam. Weak moves like that tend to get much wider coverage. Thunderbolt is far more focused to Electric types, with some exceptions like Dragonite, Gardevoir, and Latias. Ice Beam would be a unique, aside from Alolan Marowak literally no fire type in the game gets that move (and Marowak gets all sorts of weird moves it can't make good use of, like Rain Dance, Thunder, and so on, Rain Dance is also quite rare on fire types). Offensive Ice moves on fire types is unheard of, it just doesn't happen. And just because Delphox is a magician doesn't mean it should get Ice Beam, other magician pokémon like Alakazam or Mismagius also don't get it.