If an app creates files on a filesystem, then they can be backed up and synced. If a message service uses an open protocol, you can use compatible clients on different devices.

The benefits of interfacing with common protocols become multiplicative. Some domains that have standard protocols to allow full multiplicity: Emails, messages, filesharing, notes, calendars, document types, schema languages

Some domains that could use better protocols: personal dictionaries

When you use protocols like this, you more or less guarentee durability and an ecosystem of compatible utilities.