Well I don’t think you should get rid of plagiarism rules simply because they aren’t enforced. To quote a favourite quote of mine:

“If you want people to respect the big rules, you have to be willing to enforce the small ones.”

By the logic of not having plagiarism rules if you don’t enforce them, the fact that people commit murder means that we should abolish all laws against murder.

You have to enforce them and passing more laws doesn’t solve the problem. As I’ve said in other situations, you can pass the “lobbying is illegal act” all you want but if the people they apply to don’t follow them, it doesn’t matter how many times you pass a law against lobbying, or plagiarism, or murder.