The difference of a private chat with an Ai to a public question on Stack Overflow (or any forum for that matter) is, that on Stack Overflow multiple persons can read and comment. Answers often iterate and fact check if someone hallucinates, because so many eyes sees it. If the answers are helpful is something everyone has to decide themselves, but the principle of an open platform being very useful is undeniable.

Compare this to your private Ai chatbot. Only one person sees the answer and if something hallucinated is in there or the quality of the answer is not good, then you might not know. And those Ai bots are controlled by the few big corporations, maybe a little less if you use a custom offline bot, but they are probably not as good as the big models. That's why this is a bad trend. I think the open and user controlled Stack Overflow was a better approach, by principle.