Dear Deanna,
Good day! Thank you for posting in Microsoft Community. We are happy to help you.
According to your description, you copy a list from Create List > From existing list, it doesn't bring in the data, only brings the column titles.
As mentioned in these articles Create a list (microsoft.com)
Create a new list based on the columns in another list (microsoft.com)
When we create a new list by using the option From existing list, the list structure is copied, however, the actual content of the original list isn't copied.
We do understand the inconvenience caused and apologize for it.
It would definitely ideal if we can copy all content from the original list when using the From existing list option. Personally, I agree with you, this is indeed a good addition to the current features of SharePoint list. I took the liberty of creating an entry in our Feedback Community Ability to copy all data of a list by create a new list From existing list, I suggest you vote for it and encourage your team to do the same. Our Product Team is in-charge of the site and they are constantly checking the comments and feedback from our customer.
Thanks for your cooperation and understanding!
Hope you keep safe and healthy always!
Sincerely,
Tina | Microsoft Community Moderator
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