I think that a fair part of the public has been conditioned to see large scale corporate social media services as more legitimate and more useful than their smaller scale analogs.
More generally, a fair portion of the public is simply conditioned by ever present marketing and advertising into seeing "Big Corporation" as having more legitimacy than other options in so many things.
Consequently, I often find that "the public," as it were, has shit tastes in what it considers to be "quality."