Probably because it's based on Serena's crappy monster?But it's moveset is so rubbish, even for event stardards.
I think the only anime-inspired Pokemon that were distributed in the west were like Ash's Pidove, Iris' Axew, and Cilan's Pansage, which were all given in eggs (thus kinda defeating the point of them being someone else's). Ash's Pikachu was given away a few years after that, and never got distributed in the west. I doubt Serena's Fennekin will be.