Except that they have to provide an actual service for those points, which costs money.
Except that the incremental cost of providing those services is small whereas the incremental revenue is large, as has been discussed earlier in the thread. Qantas's fixed costs are high and sunk (cost of planes, lounges) whereas the marginal costs of providing perks to higher-status travelers (priority boarding, seat allocation and check-in, lounge and business class food & drink) are zero or low.
Two exceptions might be increased baggage allowance which, if utilised, would lead to higher fuel costs; and also increased accumulation of points, ie liabilities, for higher-tier customers. My gut feel is that not many people would take advantage of the increased baggage allowances (which, in any case, were cut way down a few months ago).
As for increased liabilities...
I think QF would rather just have a liability (that potentially just goes away by itself, if the points are allowed to expire)
I suspect one of the issues that Qantas have identified is that the liabilities aren't going away fast enough for their taste. The programme design actually makes it quite difficult for unused points to expire by themselves, which is great for customers, but would make the accountants nervous. Accountants usually prefer vouchers with a clear expiry date so that unused vouchers can be cleared off the liabilities on that date and therefore recognised as profit. QFFP points on the other hand are like voucher without an expiry date (except the asterix that clears them for no activity after 18 months), so the liability could potentially exist on their books for forever.
One of the consequences of the latest changes is that liabilities growth will slow for the long tail of customers who fly rarely and mostly fly discount economy. They could have achieved the same effect by letting unused points expire after X years on a FIFO (first-in-first-out) basis, but I'm guessing they figured that would have gone down even worse than the current changes from a PR perspective.
Interestingly, the latest changes might actually speed up liabilities growth for the higher-value customers, but then, the changes are clearly geared towards retaining that premium end of their customer base (no doubt as a result of competition from Virgin in the domestic business sector and overseas airlines in the international sector).
I'm not sure if the new tables will encourage businesses or rich travelers to spend (even) more money with Qantas on higher-priced fares, but seeing those QFF points tick over even more quickly for the fares they're buying now anyway might lead to greater lock-in, ie a "golden handcuffs" effect where one is reluctant to move to another programme where you don't have hundreds of thousands of points sitting in the bank.
To me all these changes appear to be part of an overall mindset of (a) profitability via cutting costs rather than increasing revenues and (b) protecting market share rather than growing market share.
Ironically, in my case, the double status credits and marginal ASAs were both initiatives that made me spend much more with Qantas than I ordinarily would. In other words, they were very effective as a revenue-increasing, market-share-expanding technique.
I flew Qantas even when they were up to 50% more expensive than competitors. I sometimes traveled in business whereas I ordinarily would have flown Economy. I did status runs where I flew extra legs at additional cost just to get the extra SCs. (eg SYD-MEL-PER-BNE-SYD instead of SYD-PER-SYD.) Were the DSCs and MASAs a short-cut to Platinum for me? Sure. I wouldn't have reached WP if not for them. But they were a shortcut that generated thousands of dollars in revenues and only cost them hundreds of dollars at most. What did this really cost Qantas except make them thousands of dollars in profit?
You can only claim that these incentives were "costing" Qantas profit if you (a) either assume that I would have made those same purchasing decisions, booked the same flights at the same higher prices, without them, which is definitely false in my case or (b) assume that I was taking away a seat from a full-fare paying customer which, given the low yields associated with their "65% market share at any cost" strategy is also false.