From talking to people further along the plagiarism spectrum than myself, they see it as developing good taste or almost coaching.
Yeah yeah in a writing class its hard to justify not learning to write. But in any other class...
Lets hypothetically say we're in a computer science class and our assignment is to write an essay on the supremacy of the C++ language. There's all these English department goals of becoming a better writer that would be met by my pitiful attempt to glorify polymorphism. But the C++ goal of learning to be a better C++ programmer would be best met by extensive reading and research to find the best Stroustrup quote. If I were involved in the academic scene of converting papers into salary via cooperation with other researchers, I need to quote my coworkers accurately to share the revenue appropriately. However what if I don't have the goal of playing that game? In a learning environment in casual verbal conversation I might tell my C++ instructor that C++ main() returns an int. Yet if I write that down as I just did, I'm committing the academic sin of plagiarism by not properly footnoting Stroustrup, that's a direct quote from him. But I'm not trying to play the academic game, I'm trying to learn to program, and develop good taste by copying the right people. It seems a little unfair to grade students based on playing a different game than they signed up for. Even if the institutional goal is to produce little academics, in practice almost none of the kids will become academics.
That's a very authoritarian example of copying a guy at the top; but it also applies to lower level copying.
They're not necessarily wrong or self destructive, just kids on a different path with different priorities.