Comment by everforward

It could be useful if you're doing something with the string that operates sequentially anyways (i.e. block-by-block AES, or SHA sums).

I _think_ the intended use of this is for people with bad internet connections so your UI can show data that's already been received without waiting for a full response. I.e. if their connection is 1KB/s and you send an 8KB JSON blob that's mostly a single text field, you can show them the first kilobyte after a second rather than waiting 8 seconds to get the whole blob.

At first I thought maybe it was for handling gigantic JSON blobs that you don't want to entirely load into memory, but the API looks like it still loads the whole thing into memory.