The point is that their identity as a scientist will be one small contributing factor compared to who they are as a person, making it difficult to really even answer without just going to each individual person and asking them. Hey plumbers, why do you use Facebook? Hey accountants, why are you in Instagram?

I can answer it!

Scientists aren’t a monolith and are an extremely diverse group of people associated together largely by profession alone, and within a single lab of scientists all working on the same project one could expect to fund each one using different social media if at all.

Nothing new under the sun.