There is rather deep understanding of what can and can't be copied in creative circles. Sure, unintentional copying can and does happen, but people usually make an active effort not to. This is partially thanks to the feedback loop that if you make something overly reminiscent of a particular original, it will *remind* you of that original.
In specific disciplines there is an understanding of what is a "technique" and can be learned, and what is actually an original creation and can't. As an example in music, chord progressions, musical styles, and song structures are in the public commons while melodies are not. As a musician I know full well that I can take inspiration from popular chord progressions or specific songs using them, but I can't just rip off a melody (minor references aside, and in that case it's usually very clear when something is just a homage and not an integral part of your creation) and call it original. But I *can* make a cover version and that comes with its own copyright rules. I also know that there is meaning beyond these rules, e.g. if I make a song with very similar instrumentation and structure and chord progressions to another song, but a different melody then it would be interpreted as a style parody (and the lines are a bit grey here if I try to pass it off as original, but then parody rights are their own concept).
AI just doesn't know about any of that. It's a dumb linear algebra machine that just learns patterns and associations in its training data and has zero concept of copyright, morals, common sense, or creative convention.