If I'm going to go the route of sharing a password, why wouldn't I just put a .txt or .html file with my email body in a password-protected/encrypted .7z or .zi

If I'm going to go the route of sharing a password, why wouldn't I just put a .txt or .html file with my email body in a password-protected/encrypted .7z or .zip and just send it with plain old gmail? My buddy doesn't have to change his email provider or click on any special links. In addition to not having forward secrecy (if a 3rd party gets his crypto password, they get ALL of my messages to him), this seems to fail the classic "In order to exchange a secret, first exchange a secret" crypto usability test.