I'm general, familiarity leads to apathy. When we get used to "bad" feelings, it's easy to keep choosing situations that produce those instead of good feelings.

This is how we get people who "prefer" to be sick, tired, angry, hungry, dirty, afraid, etc. -- all things humans generally don't want.

We can train ourselves to "want" to be sick or angry if we're not careful to steer things the other way. It's much easier to control people who are sick and angry (and sell them things), so most messaging in society amplifies these negative emotions.