Only foreign visitors carry cash these days in China in cities in my personal experience :-) Some shops actually don't accept cash at all - so you have to pay a colleague in cash and they'll pay the vendor with Ali or Tencent Pay on your behalf.

China netizen population is estimated around 900 million. So essentially all adults in Urban and many in rural excepting small kids. Generally for the elderly, their kids or grand kids will help.

It's also pretty easy to take an item and walk out without paying. But it doesn't happen. At least, it doesn't happen that much, and I would guess it happens much less in China than in the USA (though I'd be curious to see actual shrinkage numbers).

QR codes seem to have largely supplanted cash and credit cards in mainland China, whatever hypothetical downsides they might have. And the very limited hypothetical advantages of NFC (it's unclear to me what they actually are, but let's grant they exist) don't compensate for the fact that an expensive terminal is needed, so NFC isn't displacing QR codes in the near future.