It's because a lot of people enjoy the idea of it being "them" that's going on the journey, and customization helps with that immersion by allowing them to tailor their character's appearance to be closer to their own. It's a matter of immersion.
Exactly. Compare with being able to choose being a "boy" or a "girl". Heck, compare with being able to name your character, and your pokemon.
In addition to that, with the large online community, it's great to be able to express yourself in a way that a generic Trainer class sprite does not.
Exactly. It gives people choice. It allows a more "intimate" (not the right word to use) connection with one's in-game avatar, which truly becomes an avatar.
I never doubted why people want Trainer Customization, it is pretty clear. And I want it too.
My question is, why does it seem to be the n1 demand fans have for SM, when it isn't such a relevant feature in terms of the actual gameplay.
Because they took it away in ORAS. And GF has a habit of adding features, then taking them away. And sometimes not giving them back.
How is it that we are able to take choosing boy/girl or naming our trainer for granted (we don't have to hope for these, because we know they're happening), and yet, customizing our trainer (which is only one step further) is something that we have to hope for?
Because GF has made it that way for us.
Side note: Personally, while I would like customization to come back, it's not at the top of my list. But I definitely understand why it's important to so many people.