I think part of the idea is to incentivize the centralization of stake into fewer accounts and incentivize the purchase of more stake with the new curve. I thought they got rid of dust voting threshold in the last hardfork, but I might be wrong. I still think there is a bottom arbitrary limit (something like 0.001 Steem) but I could be wrong. The economics are hard to keep track of considering all the ideas that have been tossed around the last couple of years.