You mentioned most of it, mitm, family/friend access to files, losing of devices.
Another thing most people overlooked would be in athe corporate side of things, compliance is another factor to look at. Data protection policies etc.
How about hosting your encrypted files in another person or organization's infrastructure? Cloud services is a huge thing now, AWS dodoes take measures to encrypt & safe keep-keep your data but it's best you add your own 'layer' as well!
