Read the white paper
Page 16.
This huge (exponential?) inequality is intentional, the ideology for this is given by "Zipf’s Law".

if we have a million items, then the most popular 100 will contribute a third of the total value, the next 10,000 another third, and the remaining 89,900 the final third.

I can't find the official roadmap of 2018, is there anything that could change this principles?