As someone who prefers eevee, I’m just as baffled as you are, anonymous.
Very likely because it’s cute, it can stand on its hind legs (and can therefore be put in tiny costumes), it’s bright yellow (and therefore highly visible), and human beings have an unfortunate tendency to perceive small, rodent-like creatures that invade their homes and destroy private property as lovable.
Although really, eevee are adorable, and they can be taught to do more tricks than pikachu. I just don’t understand it, to be perfectly honest.
The Pokédex According to Bill 