This.
People always ask me: where's the harm?
Privacy harms are a time-shifted risk.
The moment you are protesting against your government, a seamless cashless public transport system can turn into a data trove for surveillance crowd control.
There is usually never a line at the train ticketing machines. Judging from an overheard convo, it appears that people are reluctant to use their rechargeable Octopus cards for fear of leaving a paper trail of them having been present at the protest.