Oh come now, how do you get hold of enough cash to be immune? Keep 6 months living costs in cash in your house!?
Also, if they're turning off your bank accounts, they're turning off your utilities too... And you'll miss your car insurance payments, so you can't drive either.
Consider that it’s entirely possible to mandate that POS systems, ending machines, etc. check the serial numbers on your bills against a blacklist. Cash is no refuge if a government wants to turn enough people’s lives off badly enough.
Cashlessness makes it easier to cordon off the official economy from the blockchain/grey economy. That is assuming the blockchain is made illegal. Otherwise, I guess there isn't that much of a problem.
Also, if they're turning off your bank accounts, they're turning off your utilities too... And you'll miss your car insurance payments, so you can't drive either.