House of cards. Cashless societies mean: the unbanked are further isolated and prevented from engaging in commerce. Older generations are left behind. Just trying to switch bankid login from old phone to new phone is a PITA, and I'm tech savvy. Lack of anonymous transactions means that my banks know about my vices such as gambling, porn, or strippers. Cascading failures - payment network crashes means no one can auth…
Also anyone that's lived through a hurricane or a blackout tell you cash is king. Having a few days worth stashed is a good addition to any preparedness kit.