I have a database of say 3 GiB and plan to make a gziped backup of it. Using `VACUUM INTO` creates a copy of the original, so I need another 3 GiB of space. Plus when creating the backup additionally the gziped size for the backup itself... On an embedded device that can matter. If I can gzip the active database directly, the main database can grow much more before I ran into space problems. Plus it saves some write cycles on the flash media.