Just read that Henry II of England crowned his own son King but just as a title with little power. What reason would Henry II do this for?

1. Henry II had taken power after a long and grueling civil war. Crowning his son king before his own death was a way to emphasize that the Plantagenets were here to stay. 

2. Henry II was notorious for playing mindgames with his kids. This was a way to give Richard just enough of what he wanted without giving him what he actually needed.