First, the origin and ultimate reason for the brain’s existence is not to help us think or feel or create art, but to control the movement of the body.
We tend to be impressed by the “higher” functions of the brain, such as its ability to think, feel, empathize, or create art or science. However, the brain was evolving for a long time before it developed any of these functions, and it spent much of that time working on better movement – movement with more precision, differentiation, and sophistication. It’s a very hard engineering problem to control a body with many degrees of freedom, and the brain’s accomplishments in that regard are in many ways more impressive than its abstract reasoning abilities.
For example, as pointed out by Wolpert, we have created a computer program that can beat the world’s greatest chess players, but cannot build a robot that can pick up a piece and move it from square to square. Computer programs can compose credible symphonies, destroy KenJen in Jeopardy, and carry on conversations that seem very human. But no robots can even come close to the movement skill of a three year old in walking from place to place, picking up objects, and performing other simple movements we completely take for granted.
The same thing happens while we row. We are constantly adapting to a moving boat, not perfect consistent water conditions and not perfect consistent teammates. Our brain needs to process all these changes all the time and adapt and react to them. Concentration in rowing and to move correctly is key to efficient rowing.