Who is tipping in Shenzhen?

Just got out of a massage place and at the end 4 guys rubbed down my feet my back and put on my socks and shoes and with each passing working they called them to help saying he is American in Mandarin. I am ABC and understand but don’t speak well. At the end they gave me water with a tray with QR code and they huddle over me asking for tips. I was very surprise at this as I didn’t expect this. When did this started? Did tipping culture found its way to China too?