We’re naturally inquisitive creatures, though. That’s how we got here, by asking questions that matter to us. Why should we handwave away the most important question of all time? Would you be satisfied if the answer to every important scientific and philosophical question was “It doesn’t matter, don’t worry about it”?
Morality is not at all self-evident. “Basic empathy” is such a vague concept that it can be turned in any number of ways. Is it more empathetic to force someone to be born against their will and persist in this world full of suffering, or to kill them before they’re born so they never have to suffer? Ask a hundred people a list of everything “basic empathy” covers, and you’d get a hundred different answers. As for the religious caricatures you mention, of the hundreds of religious people I know, none of them “want to do a bunch of heinous things were it not for the idea of hell.” They want to do good things, instead, out of love for the Lord who created them. Based on articles like the one above, though, people refusing to believe that morality is imposed makes them come off as wanting to do whatever they want and then retroactively rewrite their morality to make it seem like they’re doing good things. Look at any 20th-century dictatorship and you’ll see what I mean.
Some people are simply too dangerous to be left in society, but unable to stand trial. That’s why we have solutions like this.