Is your question why competition isn't strong enough against market-dominating incumbents to effect change, or why the named companies don't need the customers or service providers they expunge?
I see. The parent's "effect change" was that the banned or disaffected customers, even if they use other services, will not damage the market position of the service they were banned from or left.
I.e., Facebook doesn't have to care that you send emails and make phone calls instead of Facebook messages, because your individual contribution to their income is negligible, and, I suppose, you don't represent a pervasive or effective force in their target demographics.
What parent's effect change? You were the first to use that expression in this thread.
will not damage the market position of the service they were banned from or left.
We weren't talking about their market position, but whether customers had recourse, and I said they have in the form of competing services.
But if we're going to discuss the effects that an individual can have in changing overall practices of an organization, I'm not sure if public institutions will come out very well in the picture.