I gave you a perfectly good, practical benefit to bringing it back: TO MAKE PEOPLE PAY!
This sounds facetious. But taking it seriously anyway, there are still only two types of users: first, those who don't take rep too seriously, in which case you're not making them "pay." Second, those who do take it seriously, in which case rep starts fights.
And isn't this having it both ways? You can't make fun of people for taking neg rep too seriously and then use that same fact to argue for keeping it.
But seriously (even though I was serious above) by that logic there's no real practical benefit of having plus rep either. What good does it do? Nothing. "It makes me feel good about myself." Delusions.
Because the things positive and negative rep supplant are not identical. Positive rep replaces "Me too!" or "Totally agree!" posts. Agreement, by its very nature, is more homogeneous than disagreement, and can be replaced with a simple points system which cuts down on needless posts without losing much.
Disagreement, on the other hand, has something to add by its very nature, which means it has to be expressed in words. And differences in taste and opinion are arguably the entire point of a site like this. They're what expand our horizons and refine our tastes. So a system that replaces that process is costing us far more, collectively, than one that replaces simple agreement. Agreement is the end of the process; disagreement is the beginning.
And there's also the simple fact that one makes people happier and one makes people angrier. And what's delusional about being glad that people like what you said, anyway?