I have unlimited storage, but find compressing pictures and videos useful, as I have a slow download/upload speed, and that many of my media file don’t need to be uncompressed. I know that they can be split up, but it’s not always enough.
Being able to selectively compress files or folders (I guess there wouldn’t be a way to reverse it) would he great.
Generally video and image formats don’t compress too well because they are (typically) already in a compressed format, Re-compressing doesn’t gain much storage benefit, and can sometimes be worse.