Have you actually used it?
It's the most basic possible website, API, and app for a language model AI. It's barely functional. For example, the iOS app couldn't even display images until the other day.
> There are a million little decisions that go into a runaway success like this.
I agree that GPT-4 is amazing and probably the best. But there are several other competing implementations of language model AIs right now, some are even developed as open source.