I guess it's a neat psychological trick like airline points
With very minimal effort you can literally have an effective 25% rebate on all flights.
Let me put it this way, you might get a 25% cashback on a 1000 flight, but there might be a 500 flight alternative from another lowcost competing airline which you didn't even consider or knew it existed due to their points moat or whatever
You're basically giving your money away to the airline to keep, instead of having it in your bank account.
It's not real money, if the airline goes bankrupt tomorrow do you have your points?
[0] - https://www.bitsaboutmoney.com/archive/more-than-you-want-to...