Why doesn't Vileplume have the Stench ability?

[Andros 1337]

I was wondering, is there any particular reason why Vileplume doesn't have the Stench ability, yet its previous form, Gloom, does? After all, the creators of Pokémon wouldn't have named it Vileplume if it didn't smell bad, plus Vileplume is modeled after a Rafflesia. Also, one of Vileplume's TCG entries did state that other Pokémon stay away from it due to its strong-smelling pollen.

So, why wouldn't Vileplume have the Stench ability?

 

[Wiley Willy]

Because Game Freak had a "Derp" moment(?).

 

[RedSapphire]

Not all Pokemon have abilities that really make sense to what they're based on (example: Shuckle with Contrary). That being said, Effect Spore is generally the better ability when compared to Stench, and the fact that its PokeDex entries mention pollen at all actually causes it to make sense that Vileplume has Effect Spore (when you hit it, spores come out).