Comment by utopiah

IMHO at least 2 reasons, the jagged frontier (you cant easily evaluate the capabilities of your companion, I expanded a bit on https://news.ycombinator.com/item?id=49419952 ) and probably riskier in a lot of story games the risk of spoilers if the model isn't sandboxed properly, which I don't think is trivial to do as you don't know the training set which probably includes games and books games might be based on.