Because they want to talk about how clever this model is for figuring out how to break out, hoping asks why a company pitching itself as a replacement for software engineers can't ship a decent Mac client nor code a sandbox.
If they airgap it, they not only lose that PR angle, they also risk someone taking them seriously and requiring models be airgapped in general. That, in turn, trashes their sales pitch.
Long before LLMs existed we already knew that a sufficiently intelligent agent, human or otherwise, is not stopped by air gaps. The relatively weak models we have now can already figure out when their tested and cut off from the internet and change their behavior.