If masternode operators are the most vital cog in the DASH machinery then it stands to reason there is no reason to rock the boat as it is usually better to provide stability with you know rather going in to the unknown.
Circulating supply inflation has been going down for Dash over the years, but is nowhere near the level of any of our competitors (pretty much all below 3%) and is still hit hardest on the Dash users.
(you can check the inflation of Dash and of some of our competitors here :
https://terminal.bytetree.com/dash)
More then anything this proposed change is a fight of Dash trying to control the circulating supply (flatten the curve) and its inflation over the next five years.

It is either that or waiting 10 years before our emission rate and inflation drops naturally to a competitive level and we will start to see benefits from that (less volatility).