I basically use it to pay small amounts among private persons. E.g I was on a trip in China with colleagues, one of them stayed longer, so I gave her all my remaining CNY cash and she paid me by mobile pay. One advantage is that you only need to know the other person's phone number to have the transaction done.

Or say you're in a restaurant with people with whom you're going Dutch, one can pay the whole bill and the others reimburse him on the spot with mobile pay.

In commercial situations it MIGHT be useful in cases where MobilePay is accepted but no cards (haven't seen such, though)

Of course some evil FT'ers came up with the idea of mining points by using this method.