There are many cases where you want to use public data but it's not practical or feasible to pull it from the hosted region. In those cases, it would be better to copy the data into your own bucket which will put it alongside your compute environment, saving you costs and time in the long run.
An example use case would be copying certain files from the igenomes S3 bucket to your own AWS region or cloud provider for use with nf-core pipelines.