It's not necessary to sync history and contacts between devices in a peer-to-peer way because there is no network externality for synchronizing data. You could

It's not necessary to sync history and contacts between devices in a peer-to-peer way because there is no network externality for synchronizing data. You could use a centralized service to sync the encrypted data. If the centralized service ever does things you don't like, you can change to another centralized service or host your own, and, importantly, you can do so without being affected by what other people do. Communication platforms provide more value when they have more users, while centralized synchronization services don't provide more value because they have more users. So it's fine for synchronization services to be centralized, while it's not fine for communication platforms to be centralized.