Cashless society is a bad thing because there is no financial privacy in a cashless society. Except for crypto, if all you have is banks or other centralized electronic payment systems, all your monetary transactions will be fully traceable and censorable. When you have your money at the bank, you're really not in control. If you live in Cyprus, you will remember when the banking sector was about to collapse and money in people's accounts was frozen and all balances suffered a 10% haircut just like that to prevent the banking sector from collapsing. With crypto that cannot happen, which explains the surge in the popularity of Bitcoin in Cyprus at the time, but crypto is too volatile to store any significant amount of wealth, yet. Cash is not suitable for storing much wealth, either, but you can easily store some money in cash for weeks or months if that suits your money management style.
Also, with cash you can pay for stuff even when power is out or the Internet is down. If all you have is electronic payment systems, you will be shit out of luck if something bad happens such as exceptionally bad weather cutting off power or Internet connections.
I do not think that a cashless society would be a good thing. Up to a certain degree it might be beneficial but without cash a lot of people would loose out, especially people who do not have the means to use or afford computers or mobile phones or who do not know how to use these devices. What about elderly people? Or other people who never had the chance or saw the necessity to use computers, or those who are extremely visually impaired or those who are mentally not capable. They would miss out with catastrophic consequences.
Furthermore I do not deem it wise to make ourselves to dependent on technology and crypto....What if the whole crypto based system of a country is hacked or otherwise interrupted? That would be a desaster.