Dhein, the key is that frequent flyer programs are profitable and not just a cost centre, (as sixtyeight noted). In that case, whether you earn points via flying or via credit cards is not the main factor, I suppose.
Any business offering QF or Velocity frequent flyer points buys them from Qantas Loyalty or Velocity. Qantas/Velocity charges them more than the cost per point for a redemption. Hence why they generate huge margins.
Yes airlines want to attract flyers back with Frequent Flyer benefits. But they’ve created a valuable pseudo-currency (hence why Qantas has launched reward incentives aimed at those who earn points via credit card spend rather than flying). If they were to kill the FF program, they would be shooting themselves in the foot. Zero chance that happens (except in case of bankruptcy)