For situations where that text needs to be formatted a specific way but can't due to the platform. For example, twitter (where you can/should also include a pastebin, gist, gh repo, etc...) where having an image is better for retention/engagement

Where the code is illustrative not intended on being literal copy paste, and the sharing of text without formatting hinders readability and illustrative intent

For when you have shared your code as text but want a pretty hero image to go with it?