The risk of the payment system getting shut down and people being unable to make payments for a while is real. And it is one good reason to be less reliant on digital payments.

But there is also the risk of bad actors, which could also be e.g. Russia, getting access to decades of payment history through a hack, if everything is digital. Having that data for every citizen of a country could enable efficient profiling of people in the country using big data analysis technologies.

The kind of thing you could find out with the transaction data is who are working in the military or security police, who is sympathetic to Russia and at the same time vulnerable to work with foreign governments, and potential blackmailing material relating to people in these or other groups. I’m sure the analysts working for the bad actor can come up with even more useful things to look for in the data.

There are of course a lot of other data sources that bad actors are interested in and that are easier to hack, but the financial history seems more comprehensive source of information than most other ones.

If you are using Mastercard in the US, Google will be getting transaction data all the same: https://www.bbc.com/news/technology-45368040