There are several threads on this already, but the basics is this business makes money by selling points, first and foremost to QF, and then to the other companies.
Now this is effectively gives them free access to that money to invest as they like until the point is used. Now here is the best part for them, if the point is never used, they get to keep the full cost of the the purchase of that point, which is one of the reasons why the number of months that they would hold onto a unused account went from 36 down to 18, it effectively gives them free money.
Things like ASA's where the number of points required to redeem a seat are beyond stupid (eg 700,000 for a J seat SYD-HGK, where as the next day the same seat is only 80,000) means that they are effectively buying the seat cheap from the airline, selling the seat at a very expensive rate to the customer, and pocketing the difference.