I though that I clarified it to you, but you still don't understand that there is difference between right-footed player and left-footed. And it seems that you are out of arguments, repeating same sentence over and over again. So once again:
"On the highest level, every single mistake matters. And even if you are so skillful to use your both feet perfectly there is still difference between your better leg and weaker leg. That's why it's more convenient to run with the ball using better leg, you have better control of the ball, there is lower chance to make mistake and lose possesion. That's why it matters, coach.
Chech videos on YT or turn on TV to watch Bayern, City, Borussia or Real. Why do you think Ribery is deployed as left winger and Robben as right winger? They are not skillful enough or it really matters if you are left-footed or right-footed?"