These companies absolutely do have people who's job it is to sit on social media and promote these products, its marketing 101
> who's job it is to sit on social media and promote these products
Oh shit, I didn't know Marketing exists! Different thing from what OP described.
Having worked at multiple large companies more often than not the truth is there are 5 levels of approval for every tweet that goes out and writing a single blog post can take months.
The smart companies out source their gorilla marketing to a third party, having realized their own inadequacies.