The thing about an ancient language on clay tablets is that you can get the translation wrong so you want to keep the things around incase you have to do the translation over again. Digital data can be moved from one format to another so there is no reason to keep the old media unless you lose the HD you keep the data on.
The same applies for clay tablets. Most of the modern work has been from scans of tablets, using enhancement on the images. The original becomes irrelevant.