Espionage for the sake of espionage isn't useful. But if you're collecting lots and lots of data about what people like and what makes them angry and you have a direct line to feed them whatever information you want, having tens of millions of targets for opinion-influencing content is a very powerful tool for a state actor.
Contrary to facebook where people would literally "Follow" their political parties, workplaces, friend groups from school/work/gym/life, etc.