I don't understand the planning around "lifeboats" and the ISS. I thought that there was always an extra Soyuz capsule docked in case people are stranded on the ISS. Yet, it's never been used and it's never discussed as an option.

Even with Columbia and after, the discussion was always around sending a second shuttle up if the backflip inspection found a damaged heat shield. Maybe that's more understandable given the number of people involved on the Shuttle.

Still... What's the purpose of having that lifeboat there if it's never considered?