My best guess is that it’s useful, if you specifically just have a snippet of text you want rephrased. Like, imagine you find a paper you want to plagiarize, so you copy some text, paste it into Notepad, click the rewrite-button, and then you can take it from there and paste it into your LaTeX editor. In some sense, Notepad is the minimal UI you need for that, which also starts up quickly.
My best guess is that it’s useful, if you specifically just have a snippet of text you want rephrased. Like, imagine you find a paper you want to plagiarize, so you copy some text, paste it into Notepad, click the rewrite-button, and then you can take it from there and paste it into your LaTeX editor. In some sense, Notepad is the minimal UI you need for that, which also starts up quickly.