It seems to me that due to her known work ethics, everyone knows that she releases yearly, and so, producer are constantly working on songs to submit to her, selling them to other artists once the tracks are left in the cutting room.
That way, since 2010 we have been being served Rihanna's left over here and there, and in 2013/14 this situation is reaching an unprecedent limit.
"We Can't Stop" was written with Rihanna in mind, "Come & Get It" was an outtake from Talk That Talk, Celine & Fantasia singles were outtakes from Unapologetic, "Neon Lights" was written inspired by "We Found Love", and Timber was meant to feature her at first. "Drunk In Love" sounds straight out of Rihanna's playbook, and it is extremely easy to hear her singing songs like "Cannonball" and "Chandelier".
Is almost impossible to listen to a pop song nowadays without feeling that it sound slike Rihanna, which I don't think I have ever experienced before (not even at Britney's peak).
This is no shade, I actually love Rihanna, but I feel like we are in a moment in which her grasp over the industry has reached a point in which she owns it all.
It almost seems like she wasn't using this just as a swagger-ific hook: