Google Photos will no longer automatically back up photos and videos saved in folders created by and managed by social media apps. The decision will help you save space as well as internet resources it uses when it backs things up. Previously, Google Photos would instantly include these folders when you upload all images saved on your Android or iOS device. But now, this feature will be turned off by default. You will need to toggle "Back up & sync" on for the specific apps or folders.
According to a support page detailing the change, "People are sharing more photos and videos due to COVID-19. To save internet resources, backup & sync has been turned off for device folders created by messaging apps like WhatsApp, Messages, and Kik. You can change this anytime in settings." Those that have already been backed up and organized by social media apps won't be affected by the change.
Source: The Verge