I can't be sure, but maybe they are giving everyone their own copy so stuff like accidentally removing things people already bought doesn't happen. IANAL but i

I can't be sure, but maybe they are giving everyone their own copy so stuff like accidentally removing things people already bought doesn't happen. IANAL but it seems like this would make the data _yours_ instead of them providing it as a streaming service. Which means if they are e.g. forced by a court for whatever reason to not provide a specific song anymore (if the author plagiarised it for example), they can't take it away again from you because it's yours. If it were a simple service you could access to get a copy, they might be forced to not provide that anymore.