iCloud sync paused, please connect to power and WiFi

I recently started using an iPhone XR, and have all of my data migrated. I don’t use iCloud for storing my photos, because I have too many photos, and too little storage space in iCloud.
At the bottom of one of my screens (I think it was the settings app), I saw a message similar to the subject line of this post(I forgot the exact verbage though).

Since I only use icloud for “small things”, contacts, passwords, etc, I don’t understand why the syncing was paused, until I connect my phone to power. I don’t do full-device backups to iCloud, because upload speeds are too slow, and iCloud space is too small.

I couldn’t find any settings which controlled the sync pausing.
I had over 70% of the battery charge left.