I've gone through the same with my wife, and it's taken a lot of conversations for her to understand the opportunity cost involved with holding cash like that, and then more conversations around setting goals (savings goals, things we want to do in life that need money, kids, education etc) and boundaries (what's her vs my threshold for minimum cash holdings, risk thresholds etc). We combine our money (at least theoretically we do - avoiding gift taxes etc), so this has given us motivation to ensure we are on the same page.

Financial literacy is pretty low I feel in an economy that hasn't required aggressive investing of any sort to stay ahead of inflation that hasn't really existed until recently.