By increasing IP gained in flex matches riot has incentivized people to mess around in ranked.
I've done three placement matches, and in two of them I've had people on my team who are just there to try new stuff. A guy playing Nasus for the first time against a tryhard Riven (you can imagine how well that went) and then someone who wanted to play graves since he's free this week. He didn't get jungle so he played graves bot.
And I'm going to do the same thing once I finish my placement matches. I'm terrible at gangplank, but I want to practice and why would I give up 50% extra IP, even if it ruins someone else's rank? I like the riot is giving more IP, but I think they may not have thought this one out.