OK, I looked it up on Wikipedia. The bishop and queen were the last to have their moves set changed to the modern form in the 15th or 16th century. But even since then there have been some tweaks, such as the 3 move and 50 move rules for draws, and the orientation of the board. So you could maybe argue no balancing since the 16th century, and only a few bug fixes after that.
I had someone cheat against me the other day (without me realizing it, because I don't have the game sense to tell), then offer a draw in a clearly winning position. I guess they were trying to avoid detection, but I decided that I didn't want their handout, declined the draw offer, and resigned.
The system immediately flagged them as cheating and refunded my elo, so I guess all's well that ends well.
Not quite true. Before the ~15th century, the queen moved like the king and the pawns could only move 1 square from their starting square. These changes were made to make the game more exciting and less slow.
You are quite correct that an asymetrical game is much harder to balance.
However having identical sides and a symmetric playing field doesn't always guarantee a balanced game. For example, if one piece or position dominates all others it can lead to a lack of viable options and just one way to play, making the game uninteresting. You don't just want the players to have equal strength, you also want the universe of possible playing strategies to contain many different strong options.
Actually it has had balance changes. Chess clock for instance is a balance update between the players, but there's also been balancing between pieces. En passant and castling but also changing how the pieces work (for example bishop).
Despite the obvious symmetry of the game there's still a lot to balance.
Yes and this isn't necessary because the two sides are completely identical. No differences in pieces or terrain or anything so there's no need to change a piece to make it stronger or weaker.
It is too simple to be useful in real life: a mere 8 by 8 grid, no fog of war, no technology tree, no random map or spawn position, only 2 players, both sides exact same pieces, etc.
Eh. My last move was to tie a ballistic missile to a pawn and roll it down a pinball machine. Their move is to keep it from hitting the bottom and exploding. That would keep them occupied for a while.
Every time a piece is about to hit another, the players have to arm wrestle and the winner takes the loser's piece (if you can't arm wrestle then you lose automatically).