Understanding this question precludes one's psych-social paradigm.

For example, a strict materialist who is convinced that all that exists is the result of chemical interaction and accident cannot attach a "reason" for why we feels or care. They can only address the subject of nerves and physical senses that are involved in the experience

On the other end of the spectrum, a person who intuits or sense there is more (perhaps even what we call a spiritual aspect of reality the normal physical senses cannot perceive) would see consciousness and sensitivity as based in something else and these physical forms and systems are like a tuner the real "person" is channeled through.

I feel that living without a tendency to care or fear is a sad sociopathy in which we miss so much of life. Hold cold and meaningless life and our exciting differences of personality, culture, looks, would become....without being able to enjoy or be repulsed (of course these are extremes) how would we exist? Life would become meaningless IMO.