It's just like someone being paid monthly and uses his income to take care of his needs and important expenses without having financial issues. That doesn't mean that because he has a proper cash inflow management that his monthly income will increase automatically, if he doesn't find a means of increasing his income. Bankroll management is to enable you limit your losses and gamble responsible.
But you are minimizing your losses while playing the game. Remember that you are gambling with exposure to house edge that guarantee a lose in your side if you will play long term.
Just think the total number of losses if you will gamble without bankroll management in the long run. It’s already considered as a win if you have losses since the main goal on gambling is to have fun while profit just comes next.
It’s always based on our preference and overview on how we view gambling goal.