Think about it. Our ancestors evolved in environments where it was important to quickly determine what something was. Is that shape a human or a predator? Friend or foe? And you see it was better to make a quick, snap decision than to wait around to learn the potentially deadly truth.
For example, if you are hiding from somebody, it is better to determine that the shape you see on the horizon is that person, rather than wait for it to become more detailed (say until you see the whites of his eyes). Natural selection has favoured the genes which cause this decision-making, because humans who didn't do this were more likely to die!
So you are programmed to see intention behind almost anything. It is like looking for patterns in the clouds. The patterns are not real, but in our heads. And we do it because it is better to be safe than sorry. But just because a dot, shadow or cloud looks like it has intention, doesn't mean it really does. It takes more than dots to make the man!