also increases the cognitive load on voting
Exactly. This was also one of several reasons why the additional comment reward pool was opposed by myself and many others. We should not have to think about how much voting we're doing or how much weight we're giving to each vote, whether or power is being drained, how much it's being drained, etc. by being a normal social media user. Voting should be intuitive and almost thoughtless. A higher vote target allows for a relatively high number of votes, even from low-SP users (like new ones), without having to worry about the math behind it all and not seeing greatly diminished curation rewards because they're losing most of their voting power.
There is absolutely nothing wrong with the 40-vote target right now. Again, I ask anyone from Steemit, Inc...
Why is this change necessary?
If something is not broken or in need of a better long-term solution, then there's no reason to change it. Doing it for the sake of "equality" is a BS argument that denies what social media actually is and what this platform is based on. And in addition, it violates the K.I.S.S. principle. What ever happened to that?