The number of people who use whatsapp is an order of magnitude or more than the number of people who consciously use Google drive, as in people who know google drive exists. Even the people who have google drive, most of them have much less intimate data on it than in their private messages on WhatsApp.

If we are to take the position that all users are tech literate and should be fully in charge of how their data is used, then even Cambridge analytica wasn't bad. People explicitly gave it access to data that was accessible to them. However, the uproar proves otherwise. People don't like it when they click yes yes and some random app has access to their social media data or messages. This is why Gmail also started requiring independent audit for all gmail apps.