I regularly use several features within ChatGPT that are well beyond a chat window. Advanced Voice, DALL-E integration, Projects, and GPTs (mostly a couple private ones I created for my own use). There are other features that I don't use, like Canvas. Perhaps the sum of these still isn't an impressive product in your eyes, but it's surely more than just a chat window.
That’s not just on macOS, and I’m pretty sure that’s a deliberate dark pattern to prevent users from taking their query to claude or gemini after gpt shits the bed.