There is some truth in the old story that Snivy were so smug they went extinct. According to the traditional tale, no matter what hardship they faced, Snivy responded only with arrogance, confident that they could not be defeated. They would fight back against predators that they could easily escape; when tall grass was cut down and used for agriculture, they would return to the same spot, uncaring that they had no camouflage in open fields, and became an easy target. And to make matters worse, the very contempt and arrogance with which they treated potential threats saw said threats crush said Snivy just to illustrate their superior strength.
This story is true only if one recognizes that words like "predators" and "threats" in this context refer exclusively to mankind. In the wild, Snivy's arrogance is actually a defense mechanism; most predators will seek easier prey when faced with such supreme confidence, never realizing it to be a bluff. Humans, however, find nothing to be quite as terrifying as having their mastery of the Earth challenged, and have therefore considered Snivy for most of their history to be a particularly obnoxious species of weed, a relic of the wilderness which stubbornly refused to be cleared away for the march of civilization.
Yet within the previous century, the prospect of such beloved pokemon as Braviary disappearing saw the issue of pokemon extinction enter Unova's national consciousness. It was too late to save the wild Snivy, but this proud species of pokemon survives in many pokeballs and research labs. Some pokemon professors have controversially used the Snivy as a challenge for neophyte trainers, reasoning that if they could learn to tame their Snivy, they would become able to tame any pokemon.