When switching costs are high, services can be changed in ways that you dislike without losing your business. The higher the switching costs, the more a company can abuse you, because it knows that as bad as they’ve made things for you, you’d have to endure worse if you left.
For social media, the biggest switching cost isn’t learning the ins and outs of a new app or generating a new password: it’s the communities, family members, friends, and customers you lose when you switch away. Leaving aside the complexity of adding friends back in on a new service, there’s the even harder business of getting all those people to leave at the same time as you and go to the same place.