I'm talking about making it something that the average person would use, not the person that is going to be managing public keys manually.

It could even just be an option to "send this email encrypted" for only one-off emails, and most receivers that deal with sensitive information (banks, brokerages, insurance, etc.) would be able to receive encrypted email this way. It would be the standard way of sending encrypted messages.

Currently, the way I need to do this now with my broker is to either log in to their website and send a message through it, or use a special web-based encrypted message service. It's not a nice way of doing things.