How come not all pokemon can learn moves like Bite, Crunch, Headbutt, etc.? Barring pokemon that don’t have traditional mouths or heads, it seems like anyone should be able to learn those. Same with Rock Throw. Pick up rock, throw it. Seems simple for anyone with arms, yeah?

Although this is a new ask, I’d like to answer it right now nonetheless because it bears strong similarities to this recent ask: http://bills-pokedex.tumblr.com/post/174926370417/why-are-bite-and-crunch-dark-type-moves-biting

The short of it is that although it’s true many pokémon can bite, there’s a difference between that and the technique Bite. The latter resonates with a certain type of energy that not all pokémon know how to channel (or channel in that particular way), not to mention the subtle differences that separate how Bite is executed from the simple act of biting. (The official Pokémon League rulebook concerning what each move looks like is very specific on all matters.)

Incidentally, this also answers the question of why moves like Tackle don’t affect tangible ghost-types like mimikyu. Of course any pokémon can tackle a mimikyu; it’s just that the actual technique Tackle uses a specific type of energy that ghost-types strongly resist. Because a pokémon is leaning on these energies to do damage, of course a ghost-type’s body would respond by shrugging it off, as it were. And this seems irrelevant, but the point I’m making is that in all matters concerning moves, it’s more about the energy and specific technique, not about how simple it sounds. A Tackle (or a Bite or a Rock Throw) is not the same thing as a tackle (or a bite or a rock throw) until the subtle details are present.