One of the problems with a cashless society is that the banks aren't required to give you a bank account. If none of the banks will give you a bank account, and there's no such thing as cash... then you're just not allowed to have money. That shouldn't be a position that it is possible to get into.
I live in an essentially cashless country, but even countries where cash is still used would be very hard to live in without a bank account, so that legislation is important.