alt Hacker News> They are a way for airlines to create value out of thin air with their own fiat currency. For the average consumer the miles create less of a pure economic efficient benefit and more of a psychic benefit - funny money bucket that accumulates to defray some trip expenses. Economically they'd be best off with an outright 2% back card.
“Saving” airline miles is definitely suboptimal, like you said, getting 2% cash back and redeeming it immediately is the optimal strategy. Money is fungible and cash depreciates.
Plus, the “deals” you have access to with airline miles are not slanted in your favor.
> Money is fungible and cash depreciates.
At least cash has the option of earning interest in a bank account, or getting invested in other instruments.
Miles can always be devalued by the airline. Some airlines like Singapore, Qatar, and United, even practise stealth devaluation by controlling the number of cheap "saver" seats released.