Then that is the way it needs to be communicated. Saying public key, private key, cryptography puts a dumb look on people and they shrug their shoulders and say "my bank card works good enough, simpler too."
Why do operating systems have GUIs? Cause 99% of the people who use computers can't and won't use a command line. No difference here. The private key is the private key regardless, doesn't have to be called that though. Why can't it be referred to as the "pin"? That is what 99.9% of the rest of the world could relate to it as. Sometimes I do ponder the idea that folks don't really want it to go mainstream. They want to keep it "techy" to keep it their own.
Like @BoB said, it is not on them to learn this. There is a system in place that they are already familiar and comfortable with. Why on earth would they want to use a process that is many times more complicated with no forgiveness for a mistake? They never will.
Not to mention the fact if a "new user" got on to a crypto forum and referred to their private key as a "pin" code, they would be ridiculed and mocked to no end. Adoption could be achieved if it is wanted, I am just not convinced that is so.
That being said, I will keep fighting the good fight.