I’d disagree to say “not always, but it’s pretty typical”.

IMO it’s better to research one’s options, then call (particularly if one’s at an outlying airport with contract personnel and has any status) or ask for reaccommodation on specific flights that will both do the job and have available seats (using ExpertFlyer or TripIt Pro, for instance). I think Air Canada and British Airways offer a nonstop to LHR from Calgary, for instance (and later, request Original Routing Credit).