you have a sense of privacy in public, a lot more than in a space with a set group of people that you have to constantly interact with. in a cafe nobody cares how "busy" you look, you're just getting stuff done, in an office it quickly becomes about appearances, or leaving only after your boss left even if you're no longer productive, etc. basically in a public space people can "judge" what you're doing but it doesn't matter while in a private space people "judge" you and it matters.