Imagine being Box Art Legendaries.

You get shafted for the majority of the game as a vehicle. You can't even attack in that Form, you are an all-in-one Poke Ride stored as an key item within the Player's Bag.
You will be not remembered for the history of region you're in. You will not be remembered as a guidance or assistance like Rotom-dex with in-battle perks. You are just an item given to you at the start of the game, while watching the team of your owner becoming more relevant and stronger than the effort put into you might be worth it.

Imagine being Koreidon and Miraidon, Legendary Transportions since the past and in the future.