I'm pretty sure wealth doesn't follow an exponential distribution. Power law, log normal or stretched exponential or maybe some sort of generalized Zipf.
So yeah before we say: "it always looks like this, it's just about what the parameters are", we need to measure it and have a clearer idea of what it looks like in different societies otherwise we won't be able to decide what the desirable parameters are like.
Doing so conveys sloppy thinking while pretending to be rigorous only on the surface.