You know, this time, I'll bite.
Because it's a democracy and because I say so. That's all the reason I need in a democracy to push my idea out there, because I want it, I want a world with less disparity in how resources are distributed.
Not, mind you, because I think I'd come out on top, or in my case, even ahead (I wouldn't, under any redistributive scheme) but because there's millions of my fellow citizens who I think would come out a lot better in a less disparate world.
It seems like something's wrong in the world when people can work full-time jobs and need food stamps and rent support. That's all the reason I need to push for reduced inequality.
It seems like something's wrong in a world where billionaires pay a lower effective tax rate than their secretaries. That too is all the reason I need to push for reduced inequality.
At the end of the day, I'm not looking for natural laws that delineate winners and losers, I'm just looking at human-made systems that generate enough food for us all to be morbidly obese, and distribute it so poorly that a measurable proportion of my nation's children go hungry. I'm looking at that stuff and saying nope, gonna use my vote to make something else happen.
That's all, because it's a democracy and because I say so.