>>43499695A big part of it is because of the way it was first introduced. You can catch a Ralts very early in RS, before you even get to the first gym. It was rare and hard to catch because of teleport, which made it seem special, and psychic is a cool type. A lot of people, like myself, caught one and had it with them for the whole game. Personally, I didn't really like any of the starters at the time, and once Ralts learned Confusion I boxed Torchic and never looked back. Ralts functionally WAS my starter, and I'd bet a lot of people played the game the same way.
Funny thing was, I didn't care much for it at first. I just wanted to catch everything on the route, then kept it around because, eh, early psychic, never really used those much, might be useful. Then it just started rolling over everything and turned into one of my favorites.
The addition of a secondary type in Fairy, Gallade's creation, and Megas for both of them has kept it fairly firmly in peoples minds, plus it got appearances in Mystery Dungeon and Pokken. Nintendo knows it's a flagship creature, and it's treated accordingly. They'd probably like to use it more, if anything, but the fact that there's also SO MUCH porn of it keeps it from being truly brought into the mainstream.
