If you were one of the people who just gave Google Photos a chance and then decided to remove it afterwards, make sure that you also turn the photo backup off in your Google settings. If you don't, your photos will continue to sync to the app service. Writer David A. Arnott found this out when he saw his photos on his Google Photos even when he had already deleted all those photos and removed the app from his phone.
If you expect that the backup settings is on that third party app, that's where you are wrong. Rather than having the apps settings on the app itself, Google Photos uses the phone's local settings that is universal to all of Android Google's settings. So if you have set your Google Photos app to upload all new pictures to the cloud, you will continue to have your pictures uploaded to the app.
This panic coming from its users is generally caused by their fear for their security. It is not really because they have something fishy on their phone's gallery, it's just that no one wants to have their private files be accessible to strangers without their permission, even if those strangers are simply the app developers. It is indeed scary if people can access our files and know what we are up too, real-time. It is okay if we allow them to do this, at least we are always conscious about this syncing. If we have deleted the files and expect everything to be deleted, and later find out the syncing keeps going on, it would definitely feel creepy.
However in general, photo storage such as the cloud is practically convenient. It is great for keeping your photos and make it very accessible to you. You just got to remain informed about all your apps' behavior so you can save yourself from shock and panic in the future. Google Photos supposedly uses complex public URLs for you photos. This is scary for some but a Google Photos engineer assured people that it is very safe and the URLs are even harder to guess than your passwords.
