I've seen a lot of brides complain about guests who RSVPed "yes" not showing up the day of the wedding. It seems possible for an in-town guest to just forget or decide they have something more important to do, but not someone who booked hotel rooms and possibly a flight. Medical emergencies are the only cases I can think of where it would make sense, and hopefully those are rare.
In your experience, how often do out-of-town guests no-show?