Here's an answer based on anecdotal experience; I know maybe a dozen people who have a Yahoo email address and use Yahoo as their browser home page. All of them

Here's an answer based on anecdotal experience; I know maybe a dozen people who have a Yahoo email address and use Yahoo as their browser home page. All of them are of my parents' generation. I think the answer to "what is working" is that Yahoo was able to acquire millions of users back in the late 90's when Yahoo was the only game in town, and many of these users are baby boomers who get very frustrated with new technology, who are familiar with the Yahoo UI due to nearly two decades of interacting with it, and who view switching to Gmail or whatever else as a hassle that is just not worth the frustration of learning how to use another platform.