The reason a very small subset of users love it*
All the downloads making it the top app in the app stores are from people using their centralized service. The people behind these downloads have no clue that you can run it locally or can even start to understand what that would even mean. It is this usage the article is addressing.
Like the thread starter, I am also confused to why this in particular draws so much hate.
That's simple and smart. I had played around with the thought of storing encrypted versions of my password manager vault freely available, and making the password a Ceasar cipher of the first letters of each chapter of some book I am sure to find freely online. Not so simple and smart, but at least some fun. Except maybe when you actually need to use it.