There is a reason a book has no duplicate pages and a machine has no duplicate parts. They’re not needed.

This is just how search engines view content. It’s not very usable or informative for search results pages to contain multiple copies of the same thing.   This is why your website may not be listed if a search query turns up other pages with content exactly like yours.  However, there are grey areas to this, and you may not be aware it’s even happening to you.