Interesting point on what we ought to receive on spend - if you're spending on CC's with flexible reward programs, you might get between 0.6-1.2c per $1 if redeeming for gift cards, (similar to QF ofc). And of course, transferring to airlines/hotels can get you more. But then you trade flexibility - what's the price of that?
Some food chain programs can be alot better than just gift cards - McDonald's loyalty program, allows you to get an 80c Vanilla soft serve for spending $20 (4% return). And the local coffee shop or barber shop offers of buy 10, get 1 free is effectively a 10% return.
Interestingly, since you get 800 QF points for flying SYD-BNE one-way in Economy on a cash fare - if you flew this 10 times, you have enough points for a CR on the same route. This means you're getting around 7% return on spend with Qantas, assuming that all fares are $159, and taxes are ~$40. Most people would be okay with that kind of return on spend, in percentage terms. Of course, this is a specific example that changes when there isn't classic reward availability, and Classic+ would not be nearly as good value, but also consider that the cost of acquiring points is generally a lot less than actually flying.
I still maintain though that despite their pretty ordinary treatment of customers (to put it lightly), Qantas and every other frequent flyer program doesn't and shouldn't promise you'll get Business or First Class flights when you want, where you want. Social media influencers, not the airline, sell this, and people buy it, because it's such an easy sell. All airlines do is say you can get rewards for your spending with us, which is completely true. An Economy Class flight from Sydney to Brisbane is still a reward, and still saves you money. But it's not aspirational, so people don't care if it's offered or not.