They are in everywhere. This together with the use of Wechat creates a digital scenario where nobody uses real money. Even money is not accepted in some shops.
Street vendors use this technology and save a lot of time. It's much more hygienic. Better for everyone.
It's also used for publicity, etc. I suggest placing a QR code in Mao's forehead, in his official portrait, linked to his red book or whatever other lectures.