This is one of main reasons why we usually see perma bans due to plagiarism on newbies, or lower rank members. Higher rank members known the rules well, and they don't stupid enough to intentionally violate that rule.
Another possibility is that the 'plagiarism' post from those high-ranked users are hard to be found (maybe he did that when he's still newbie). But yeah, it's definitely a waste of time when you finally ranked up but then you got banned because plagiarism when you're still Jr. Member.