Balance in games is an incredibly hard thing to get right. As even in bored games you can still gain an advantage by which turn you start with. Such as the first turn advantage in chess. This complexity increases with video games as it is possible to scale up the world. Balance can also come at the cost of fun.
In a perfectly balanced game it is possible that it comes to grow stale. Balance in a video game is not equivalent to equality in character builds. If both players have the same opportunities and of equal skill it would be in their best interest to play as conservatively as possible. They would never gain an advantage or the perception of one which is important part to make a game fun. One example of this approach is 2fort sniper matches in TF2. Where it is a game more of reaction time vs anything else. A similar experience can be gained by 2 players dropping a ruler and trying to catch it faster.
Thus, imbalance is where fun is generated. It is possible have imbalance as a feature such as in Europa Universalis IV. Where each starting nation has its own unique set of challenges to overcome. But there are clearly easier nations to play as.
Imbalance is usually represented in a rock-paper-scissors type scenario. Where a player would have an advantage over one or the other. Balance comes in making sure all the scenarios all have an equal fighting chance over the other. Otherwise, there would be a meta defining game play which would all players would flock to in which you get stale game play. Even if the game play trends to the equaling of each player it is in the entropy that would still cause a game to be interesting. Such is the case with competitive Quake 3 as the starting position has players forcing to move as their opponent’s starting position has the counter to their advantage. However, each player trends towards an power quality although there is sufficient entropy in which skill differences are able to determine the match. 

Source: https://www.youtube.com/watch?v=ii_Q4OCoHvU