Actually, we engage in mind-reading all the time, just not the psychic variety. We don't experience other people's motives firsthand, but we do predict human (and some animal) behaviour by positing other people's (or animals') motives based on patterns in their previous actions or in their body language or social status. If we didn't do so, we wouldn't understand each other as minds or as people, and if we didn't do that, we wouldn't have society.