Why is there data in the games for the Fairy Gem even though it is an unobtainable item?

Question

And most of the type gems in general. What is the point?

Comments

Game Freak wants to troll fairy attack users by promising to release the fairy gem but never really releasing it.

Answer 1

the non-fairy element gems could be transfered from previous gens. (gen 5 for instance were they could be obtained in caves) if there was no code for them it would most likely create some kind of missingno item. there may be an event for a Pokemon holding fairy gem in the future, or something like that. the reason it's coded is so it CAN exist.
for instance: marshadow is coded into the gen 7 games so it can exist when it is released, even though it is unobtainable right now.

---

Edited by request of OP:

They're probably in the game right now so that the game doesn't poop itself if someone hacks them in (similar to Shiny-locked Pokémon still having Shiny sprites).

Comments

The rest of your answer makes sense, but it's impossible to Poké Bank the gems from Gen V to later games. They're probably in the game right now so that the game doesn't poop itself if someone hacks them in (similar to Shiny-locked Pokémon still having Shiny sprites).

---

they're in gen 6 as well. that was just an example.

---

my vigoroth has a normal gem for instance

---

Normal is the only gem available.

---

good enough.