Multiple Duplicate Songs in Library

First question: Why are there many questions on Apple support pages related to duplicate songs showing up in iTunes, but most if not all are as yet "unanswered"? Is it because there is no answer? I then tried using the built-in "Show Exact Duplicate" option on the iTunes menu, which certainly didn't help me, because I have MULTIPLE DUPLICATES of the same songs apparently added at the same date/time (though I didn't actually add 3 exact songs at the exact same time.) It's utterly ridiculous why the iTunes program would even list the exact song 2, 3 even 4 times. Do these work: $40 gets me TidySongs - seems awfully steep or there's a $9.99 App iMDeduper on the App Store - either way it's money to spend for something that should not happen. If anyone our there cares to actually ANSWER this question and provide guidance on 1) why it happens, 2) why it can't be rectified through Apple bug fix, and barring that the issue won't ever be fixed: 3) What is best value app to fix this "multiple duplicate songs in library" issue? Thank you.