Because there’s probably a tool call for web search, and a tool call for arbitrary code. There’s no discovery for the CLI tools it has available unless it has already chosen to run arbitrary code.

The point is that even web search should be a CLI tool, and all ChatGPT would know to do other than talk to you is how interact with a shell.

Then if you ask it what’s the time in Tokyo, it would likely reach for the POSIX date command, instead of web search, because both would be equally visible.