I get this but then in practice the only actually valuable stuff on my computer is... the code and data in my dev containers. Everything else I can download off the Internet for free at any time.
This kind of mentality, and "seems a bit excessive to sandbox a command that really just downloads arbitrary code", is why the JS ecosystem is so prone to credential theft. It's actually insane to read stuff like that said out loud.
Right but the opposite mentality winds up putting so much of the eggs in the basket of the container that it defeats a lot of the purpose of the container.