Just quoting myself from earlier:
Curation is about incentivizing stakers to actually vote on content which they believe others would agree is appealing by rewarding them for it. It's true that established authors can become very 'sticky' but this is also true for all other platforms. It can incentivize people to build a long term reputation.
Curation is a zero sum game which forces voters to compete with incrementally earlier votes over established authors and at some point you'll likely lose more due to the 15 minute curation tax timer than if you were to seek out less established authors with appealing content
Some amount of free downvotes is one mechanism that can further serve to increase mobility away from established authors, as people will be more liberal in their use to bring down posts that are overpaid, and curators over time will need to adapt their behavior if they wish to maximize their rewards.