We only ever explore the book through Winston's eyes. He FEELS trapped and scared, but how could the party possibly prevent his escape? The fields had microphones, but he wasn't GPS-tagged. Part of the purpose of the panopticon is that people don't HAVE to always be monitoring, but you never know if they are.

But I still assert he could have left. The fear just worked too well on him. Just like it's working on me. I'm too scared to quit this life and start a new one.