I think inability to include images it is actually a feature.
As long as your body is a plain text, you can present it in a very wide variety of ways and styles. Once you allow formatting and inline images, you start moving towards HTML documents, and lose consumer's control over content.
As long as your body is a plain text, you can present it in a very wide variety of ways and styles. Once you allow formatting and inline images, you start moving towards HTML documents, and lose consumer's control over content.