A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
Dear Brian Reich1
Good day! Thank you for posting to Microsoft Community. We are happy to help you
I also found this phenomenon in our tests here, which may be a flaw in PowerPoint's design.
Currently, copy and paste does not retain custom backgrounds except for duplicate slides. I completely agree with you, this is indeed a great addition to the current functionality of PowerPoint, thanks for pointing this out. Microsoft is constantly working to improve the functionality of its O365 products, and such suggestions are greatly appreciated. You can go to thefeedback community to create a new entry or vote for it.
Thanks for your cooperation.
Sincerely,
Tin | Microsoft Community Moderator