As a medium, video games need to evolve or they run the risk of becoming stale. Sure, genres stay the same, but if every publisher put out the exact iteration of every game, we'd get bored.
So there comes a time when things need mixing up; a tweak to the formula to stop gamers from getting bored and turning their backs of a once-favoured series or title.
Sometimes it's shifting the camera perspectives, to add tension by removing more of the player's immediate view. Others it's the ability to go back and discover previously inaccessible areas for more gain, or introduce an alternate approach to level completion.
Or it could be something as simple as making an action game a stealth one, or letting a character hop off of their skateboard. It doesn't have to be the biggest idea, just the best.
Yet the ire some of these features drew, usually before people had even played them, quickly shut the naysayers up when released into the wild. All the pomp and bluster dissolved, to be replaced with quiet mutterings of, "Yeah, that's actually alright, I suppose..."
Not everything works out well when put into practice, but these examples will show that the method in their madness actually worked out in the end.