Symmetric encryption is also popular and ubiquitous. I don't think this can be practically explained to most of the population of non-technical people. Encryption schemes also often use hybrids of symmetric and asymmetric encryption; they are useful for different scenarios.
Have you ever actually successfully done this? More than once? And they continue to use it?
It's a usability nightmare. https://moxie.org/blog/gpg-and-me/