Definitely see how that's a factor in many cases, but I can see other possible explanations. For example, I used to be a real serious Twitter addict, but it wasn't really FOMO driving that IMO. My own post-hoc analysis is that it was a mixture of needing feel "in control" during a period of political upheaval, alongside a desperate desire to build a personal brand and receive recognition. There's lots of people and lots of software, I think the underlying motivations are going to be different for different pairings of the two.