You misunderstand.

There is a difference between when third party content is your post and when third party content adds to your post.

If I use CC0 (public domain with no requirement to attribute) I do not source it. It is free to use without sourcing. I use gifs freely as they fall under fair use.

If I use images that are not CC0 I always source.

I NEVER make a post that is exclusive a third party piece of content and try to get rewards off their work. Any third party content always suppliments my post as fair use, but I will source so it is not assumed it is my own work.