You can now use ChatGPT without creating an account in some regions. Normally, both free and paid users of ChatGPT have to create accounts and log in to use the service. The free version of ChatGPT (GPT 3.5) is older and less advanced than the version offered to paid users (GPT 4).
Not having to log into a service offers improved privacy because you won’t be forced to associate your name or contact information (which is unique to you, thereby providing a way to track you pervasively) with your usage of the service.
However, the option to opt out of these services’ data collection practices is almost always in your account, which means you most likely won’t be able to opt out of ChatGPT’s use of your data to train their AI models if you don’t create an account. If the use of your data was opt-in, then this wouldn’t be an issue.