Concentration is a cornerstone of mindfulness practice. Your mindfulness will only be as robust as the capacity of your mind to be calm and stable. Without calmness, the mirror of mindfulness will have an agitated and choppy surface and will not be able to reflect things with any accuracy.
You can see it on the Internet now. New society demands that people share their knowledge. It's asking multimillionaires to share their money and creative people to share their creativity. Whoever doesn't share their wealth, be it knowledge, money, or creativity, will be dead.