We're big ol' experience machines. When a system's output is used as its input, that's called feedback. Cool stuff happens with feedback. Thermostats know when to turn your heater on. Microphones make big screeching noises.
People notice their behavior and if necessary, change it.
Think about it. We've all wanted something at some point in our lives. Some of us went out and got it. Some didn't even do that. It stands to reason.