There is nothing wrong with the proper use of mobile phones. They can lead to productivity (searching for solutions online), creativity (diy ideas), development of social skills (closed groups of friends on Viber with a supervising parent), etc. My 8yo sister loves googling about languages and animals and loves youtubers, but having a phone hasn't slowed her down in any way. Quite the opposite, she has been given all the tools she can get at this time and, as far as I can see, they are being used properly with absolutely no negative effect. She spends about 2h per day googling and chatting with friends who live far away and the rest of the day is spent outdoors. Ban mobiles? It might just lead to more kids using them.