The material balance means difference in material which is left *on* the board (rather than captured one).
Say, for instance,
White took 5 pawns and a Rook, while
Black took 4 pawns, a Bishop and a Knight.
Then instead of pile of the captured pawns and pieces (totally 12 elements), which would be displayed now, and not that easy to count quickly) the material balance (left on the board) would be just:
Rook + Pawn [vs] Bishop + Knight,
which is much more simple (for a human) and helps quicker evaluate position at glance.
The only useful point of displaying total number of captured pieces and pawns would the Bughouse variant (where you can use your partner's pieces) which is not the case here, otherwise it's totally useless. The material balance is much more simple, useful and intuitive approach, specially in quick games.
For example, Chessbase use this in their products, such as Chessbase itself and the Playchess client. Thank you for reading!
Say, for instance,
White took 5 pawns and a Rook, while
Black took 4 pawns, a Bishop and a Knight.
Then instead of pile of the captured pawns and pieces (totally 12 elements), which would be displayed now, and not that easy to count quickly) the material balance (left on the board) would be just:
Rook + Pawn [vs] Bishop + Knight,
which is much more simple (for a human) and helps quicker evaluate position at glance.
The only useful point of displaying total number of captured pieces and pawns would the Bughouse variant (where you can use your partner's pieces) which is not the case here, otherwise it's totally useless. The material balance is much more simple, useful and intuitive approach, specially in quick games.
For example, Chessbase use this in their products, such as Chessbase itself and the Playchess client. Thank you for reading!