[lloydjones]

Any site that gets traffic from social sharing on Twitter / Facebook.

The visits via those sources are competing with other tweets/posts in the feed. If there's a visually compelling social image, the likelihood of the URL being visited and/or shared increases.

Source: https://buzzsumo.com/blog/how-to-massively-boost-your-blog-t...

(Obviously this doesn't 'prove' that a more-visually-compelling image does better than a basic one, but it seems like it'd follow, given the inclusion of the image at all performs better than no image).