Thats true for the physics and math but some of the things are updated all the time. For example you can get a current weather report. And they have structured data about movies, TV shows, music, and notable people [1]. Every time any country has an election you’re going to retrain your model? That gets really expensive really fast.
On top of that, the training process isn’t that trustworthy. There’s no guarantee your model won’t accidentally say that e.g. Obama is the president.
All of this is to say that the best path forward is to translate questions into queries to an auditable knowledge base and then integrate the responses back into the conversation. It’s a couple years old but the best I’ve seen in this area is Retrieval Augmented Generation [2]. And even that’s imperfect, in my experience.
[1] https://www.wolframalpha.com/
[2] https://arxiv.org/abs/2005.11401