Couple of examples:
1) Certain clients insist on fully refundable tickets, so that if the planned trip doesn't happen they don't pay anything. In their strange round about way they hedge that the $2000 full Y ticket will be less expensive than 3-4 non refundable tickets if they have to reschedule several times.
2) I've known people I work with booked on several flights on several airlines on a single day on fully refundable fares - the reason? Weather. When someone absolutely positively has to be somewhere, it is a strategy that can work provided the entire airport doesn't close.