I worked at newsweek and later The Daily Beast as a web developer in charge of analytics, so I can provide some insight into this.

The product managers were under constant pressure to increase traffic, so they'd add every new feature that appeared in front of them. Facebook, comments, social crap, stock ticker (that -nearly- happened), it didn't matter. Each one of these did add a marginal amount of measurable traffic.

Here's where the analytics part kicks in. The numbers did not reflect that our readers hated all that noise, and the product managers wouldn't dare remove something that generates traffic. So no matter how pointless something was, if it generated traffic it stayed for good.