Most images on here will be non-web_source, whether this be because laziness, or overall not wanting an artist to traceback, sometimes it's just because other people don't do, so that'll rub off on people.
You aren't forced to provide your source, nor are you forced not to, it's all up to you, so don't worry about any consequences if you do or don't, most people aren't looking for a source anyways, they just want the edited image.