Civilization as we know it now would not be possible with one type of person in the world. The advent of agriculture led to humans as a whole being able to settle down and grow. From there, machination allowed us to specialize and everything you see before you was able to be created by a person who didn’t have to hunt for their own food, or build their own house.
Like creating the world we live in now, the prospect of making a playable game world is a daunting one, and more often than not, falls on the shoulders of a team rather than any individual. The successful team is the one that is coordinated, and having defined roles for each individual member of the team is a good way of organizing your group. Having designers, animators, programmers, leads, developers, producers, and owners all in one capacity or the other is required for putting a viable game to market. It helps a lot to have these various hats and the responsibilities associated with them assigned to different people, although hat juggling isn’t uncommon, and single manned project success stories are not unheard of, despite their rarity.
On my team, for instance, I wear the hat of artist, owner, and CFO. While this wasn’t originally the case, through different cuts for various reasons, it is the situation now. With the help of team mates also picking up multiple hats, we’ve managed to progress and continue on in the development of our game Mischief, despite setbacks.