Walmart's CEO, Doug McMillon, revealed on CNBC just why his company cannot take its attention away from mobile commerce. According to the Wal-Mart Stores, Inc. boss, his company’s digital business is now overwhelmingly because of mobile. “It is an incredible time of change in retail. There is a transformation going on. This move to e-commerce, the way e-commerce and stores work together, what’s happening with mobile. We knew for example this holiday [season that] mobile would be really important for us but it’s been 70% of the orders that we’ve taken through our digital business,” McMillon said.