Because that's what you're asking for, as it'd be trivial to reset the rate without accounts.
i assume they still have ip/browser fingerprint based rate limiting, but you can type in a prompt and get an answer with zero login or anything else.
Most of the current AI companies are going to fail or get bought up, so you have no idea where that account information, all your prompts and all the answers will eventually go. After social media, I don't really see any reason why anyone would trust any tech company with any sort of information, unless you really really have to. If I want to run an LLM, then I'll get one that can run on my own computer, even if that mean forgoing certain features.