The data of such a copy is nothing compared to the wider picture and the data can be used for future training, so even from a purely self interest perspective, they should be keeping the copy.

As for long term benefits, it could one day be sold as a service, once copyrights have expired on the works. We can't see it today, but that is purely the result of the law and what the law intended to do from the start, you don't see a copy unless you pay for your own.