Actually, I would think it's the reverse. Hippopotas and Snover have survivability with Eviolite+ Slack Off/Leech Seed. Vulpix has no recovery aside from Rest and Dream Eater (which are lol.) No matter the case, they aren't being banned for their own talents- just the weather. Vulpix isn't likely to stay in against Blastoise, etc, especially with a team full of Chlorophyll sweepers.