A->B->C can be cheaper than B->C. If people could skip flight A, then people already in B would buy the cheaper A->B->C.
But why would they cancel B-A when there’s a no show for A-B? More so when there’s a few days gap between A-B and B-A? The only issue being they were booked as a single itinerary/PNR. I don’t see what cost has got anything to do with it.
- Last minute travellers (who pay significantly higher for this)
- move their own personnel from B to A
- alleviating problems caused by overbooking, canceled flights, delayed flights or any other disruption.
A->B->C can be cheaper than B->C. If people could skip flight A, then people already in B would buy the cheaper A->B->C.