Why should you even care about your own personal survival and comfort? Obviously most people do, but that's a far cry from should.
Even if God exists, why should you do what he commands? Even if the answer is back to "because he will punish you if you don't", why should I avoid punishment? That is, come back to the first question up there: why should I care about my own personal survival and comfort?
Most people do care about their own personal survival and comfort, sure. But then a lot of people just do have empathy for others too. Then again, a lot of people do get sadistic pleasure from hurting others too —sometimes the same people as have empathy for others too, just in different circumstances. And a lot of people probably would obey the commands of something they considered God, if not just to avoid punishment, then just because a lot of people just do obey supposed authorities, whether they should or not. (Look at the Stanford Prison Experiment. Or the Nazis who were "just following orders").
Asking what people do do isn't going to tell us anything about what they should do, and when you start asking what people should do and why, "God says so" doesn't really add much to the conversation. Maybe we'd better take a few steps back and start asked what exactly "should" even means, and how the heck we're supposed to assess the truth or falsity of "should" propositions in the first place.