The field is too young to know what will keep users, but there are definitely things that plausibly could create a lock-in effect. I mentioned one ("ChatGPT knows me") which could grow over time as people have shared more of themselves with ChatGPT. There's also pilots of multi-person chats, and the social elements in Sora. Some people already feel compelled to stick to the "person" they're comfortable talking to. The chance of OpenAI finding something isn't zero.