The use case for this is for those things the shell cannot autocomplete. For example, you might want to get a directory listing with ls and then operate on one

The use case for this is for those things the shell cannot autocomplete. For example, you might want to get a directory listing with ls and then operate on one of the filenames that it outputs. You can retype the filename, which is error-prone, copy-paste it with the mouse (which takes your hands off the keyboard), or type the first few letters and autocomplete. Autocomplete is by far the fastest way to do this.