"No store ever turns down cash."
It's a question of convenience. I was just in a food court. The guy at the dumpling stall was happy to take Weixin. But I don't have it to give, so I had to walk back to the counter at the entrance, identify the stall and state the amount, get a ticket and then head back to the dumpling stall with it. A quick swipe with my phone would have been so much faster and easier.
And while I haven't done a formal survey, I have a sense that many restaurants no longer take bank cards, but are happy with Weixin or Alipay.
Food courts often have a place you can buy a card, which you can tap at the restaurants there