When people hear voices how come they always tell them to do bad things?

I think it just depends on how one is listening. For instance, if I listen to the monster (depression) in my mind she will continue to churn up negatives until I cave. BUT...if I stay mindful and listen to my heart, I tend to stay upright and able to give more of myself. It's just one of those battles we all fight from time to time.

Well people do hear voices like that*, but it doesn't lead to crimes or newsworthy things, so it's not generally held up for popular revulsion

*e.g. Mother Teresa

Maybe they do, perhaps we only hear about the bad ones. People are motivated to good things all the time.

Because the people hearing voices telling them to do good things, they just go about their business.