Cashless

I exchanged some cash to use while travelling in another country - trying to save on foreign exchange conversion fees charged by my credit card provider. It soon became apparent to me that this was an inconvenience to others. We are so used to the cashless world that people struggle to give me back the correct change. There has been occasions when I have received the wrong change even with the help of the till and the use of a mobile mobile phone. LOL, how did that happen?

What happened to our mental math skills? Has math become difficult these days? Will we ever so rely on machines and AI from here onwards? Will this affect our brain functions?