Anyway, they don't allow email signups, either. You have to use a social media login. So the pie gets even smaller.
Edit: also the logo is not displaying properly on the signing page (Firefox, linux)
The first is that OpenAI has rate limits. They are especially small for GPT-4, which for anything complicated can be quite a lot better than 3.5.
The other one is that if you do leave it open, then you can be sure that a significant portion of your customers will be from countries that could not pass the OpenAI phone verification. Or just didn't want to identify themselves. For some reason.
Combine that with something that scares some people a lot like autonomous AI or connecting them to servers or the internet, and it feels like you might be on thin ice with OpenAI or some regulatory group. Especially if a bunch of Russian and Chinese users are finding you on some directory or post listed as a way to get around the phone verification.
Just based on experience running my own service.