Because the amount anyone would actually pay is substantially below cost for most routes, but it's still a service that many people depend on (either directly or by the indirect economic impact of travel). It's a genuine force multiplier that is unaffordable without being subsidized; making it a utility would just shift the subsidy from credit card points programs to the government.
If airlines didn’t exist, people and goods would continue to move around the globe as they have done for thousands of years. There’s nothing magical about air travel (or any other transport mode) that makes it worthy of subsidy .
> indirect economic impact of travel
Like what?
Nearly all 'goods' are going to travel more efficiently by rail and truck. And I say nearly all to cover the outliers like maybe an organ flying across country for transplant.
So if it's not the distribution method of choice for goods, then leisure? It's probably a global positive if people fly less. People will end up going to more local vacation destinations instead of aggregating all of those resources into a few popular locations that end up being massively overcrowded. This in turn reduces carbon impact because driving 3 hours is significantly less impactful than flying for 3 hours.
If you are just talking about all of the labor that has built up to support this inefficient and wasteful enterprise, that's probably for the best to reallocate that labor elsewhere. It will happen eventually, unless you think cheap oil is a permamenent feature, so why not happen sooner than later?
> the amount anyone would actually pay is [...]
That's.... like a pretty shocking erasure of the idea of a demand curve given the forum here.
To be glib: no, that's not how it works. Increase the price and fewer people will fly, but the demand won't drop to zero. Decrease it and you make less money per ticket but the size of the market is bigger. At some point there is a local maximum, to which the market seeks.
But conditions change occasionally and the equivalent supply curve is moving rapidly because of the oil shock (i.e. it's more expensive to put planes in the air to service tickets you already sold). And things like the mess with Spirit are what happens when the market readjusts: the rest of the industry will (probably) backfill some of the lost capacity, but not all of it, and prices will (probably) rise a bit to a new equilibrium.
> Because the amount anyone would actually pay is substantially below cost for most routes
This is absolutely not true. If all the airlines were prohibited from making money with anything else (miles, credit cards) then airfares would rise across the board and there would still be plenty of demand. Not as much, but still plenty.