Manual curation takes time and effort - hopefully that effort is repaid in people then reading and voting on the best content being produced.
This is how publishing still works, with writers and agents and sub-editors and editors and, finally, publishers. The online world has merely reinforced that the whole process from creator to reader is paved, ultimately, with trust.
Apart from #Curie and #Whalepower, there is also the Minnows Accelerator Project.