The resulting annotated dataset, called ImageNet, enabled breakthroughs in machine learning that revitalized the field and ushered in a decade of progress
So, the work is beneficial, but they don't want people to know that. So by not telling people what the purpose of their job is and how necessary their work actually is for the companies that need them, they can keep it cheap and the people continue to get exploited. Terrible, but honestly, nothing new.