Because not everyone views the world the same way that you do; some people discriminate, and some even do so in hiring and other contexts where it's unlawful.

Because not everyone views the world the same way that you do; some people discriminate, and some even do so in hiring and other contexts where it's unlawful. Only thing is, that is enormously hard to tell in any particular case, especially when (as in hiring) the decision is not well-documented. Statistical analysis is helpful in those circumstances. But you can't do that unless you check what happens by random chance in your control group.