The vast majority of users absolutely don't care about data residency or "privacy", however you interpret that word. You can convince individuals to care, but good luck convincing a large group.
What can happen (and has happened) is that the existing thing becomes just toxic enough to lessen the pull and invite alternatives. For the tech communities I've been a part of this has happened a number of times in the history of the web — off the top of my head:
• ExpertsExchange -> StackOverflow
• IE 6 -> Firefox
• Twitter -> Mastodon
In all cases the migration was driven by software engineers' disgust with the platform. The current Twitter -> Mastodon migration is mostly just folks in tech, but there are enough of us to forge decent-sized communities there.
What can happen (and has happened) is that the existing thing becomes just toxic enough to lessen the pull and invite alternatives. For the tech communities I've been a part of this has happened a number of times in the history of the web — off the top of my head:
• ExpertsExchange -> StackOverflow
• IE 6 -> Firefox
• Twitter -> Mastodon
In all cases the migration was driven by software engineers' disgust with the platform. The current Twitter -> Mastodon migration is mostly just folks in tech, but there are enough of us to forge decent-sized communities there.