Facebook and Twitter are still different platforms with different origins and functions. There’s no rule that Facebook has to be a place for second-by-second breaking news coverage and reports from the ground. Nor does Facebook have any moral obligation to make force a specific news event upon its users. In fact, it is designed to do the very opposite by design: it wants to give you what you want!
A surprisingly in depth Buzzfeed article discussing the differences between Twitter and Facebook in the wake of the Ferguson protests.