Whether or not these, or any other, killings are religiously motivated could be considered relevant information.
It may be the causal factor, a contributing one, or unrelated. But it does add to the picture both the media and people watching/reading attempt to form about the perpetrators and victims.
As for the education/informing issue, it's not the media's job to teach people the reasons and causes behind something - though in an ideal world they would. They are profit-making companies who report on incidents and goings on. If they choose to offer background, great. And if that is impartial, even better.
But it's down to education systems and people's own curiosity to teach them about the world. That which I know about the religions of the world (bar Christianity, which was forced down our throats at a Church of England school, something which I fought against) I know because I have decided to learn.