Well, Read more link helps your article look short.
As it is short, it will help readers to look into the other article in the list rather than scrolling hard to reach more articles.
If you have read more link in the article,you will get more revenue,yes, when people click read more button to view a full article. It will redirect to another page with ads.As the reader want to read more articles, then more pages will form, more impressions create and simultaneously more Revenue.
Hope this helps.