My phone's predictive text says-- Hang on, let me check what dumbass thing it's going to say this time-- Apparently that I'm going to "pick up the kids for my husband" except I don't have kids and I'm not married. Predictive text is, at it's heart, the same AI working in chatGPT bots right now. Just with access to a lot more data so it doesn't make rookie mistakes like your phone's predictive text, assuming that because a lot of humans write that sentence that it must be universally true-- That everyone picks up their kids for their husbands. That's all AI it is: Predictive text on a massive scale. It predicts the most likely word that goes next, based on the words that have come before, and the structure of sentences it has studied. ChatGPT (and similar bots) are very, very good at predicting what a human would say. But that's just it: A computer program that puts the most likely word after each successive word, so the end result closely resembles human speech.
It cannot make promises because it has no concept of promises. It just knows that when the phrase "Do you promise..." comes up in a block of text, the next block of text is likely going to contain an affirmation of that promise, then a repeat of that promise, and then a statement of trustworthiness. The robot isn't promising anything, it's just simulation of a promise.
If you ask it to keep a secret, ask it to make a very simple promise, it will immediately blab that secret the moment you ask it to tell you the secret, assuming it's the kind of chatbot that "remembers" your inputs.
Please stop asking AI to weigh in on great existential questions until we have some sort of back-end working that's capable of actual cognition instead of just a word simulator for fooling your very social brain into believing that you've encountered cognition.