Great question because honestly, nothing beats more secure then a set of offline disconnected hardrives in a vault with copies at your parents/kids house vaults.

The main benefit of self hosting is accessibility.

Immich (photo server i self host) is just an app on my phone, i can upload pictures from it just like i would on many proprietary clouds.

I can equally use it to view pictures and download/share them using whatever communication app.

Immich is not connected to the internet, i need to be on my home network to use it, much safer.

I do expose a nextcloud server to the web, and gave family members an account. This way we have a secure way to share photo albums and any other files.