And yet social sciences use the scientific method; AI predictions generally don't.
Can you please clarify this point?
The social sciences are sciences; AI predictions are mainly speculative thinking by people who just put on their thinking caps and think really really hard about the future (see some of the examples in http://lesswrong.com/lw/e79/ai_timeline_prediction_data/).
An over-simplification, but an evocative one: