Jobs.
The US has a difficult position right now, and you correctly cited the cause of this problem: employers squandered their free cash, and now, they're broke.
The airline industry seems to employ about 750,000 people not counting making airplanes or services like "taxis go to the airport" or related jobs like "I make airplane fuel". That's a lot. It's fifteen times as many as work in the coal mines, to put that in Trumpian terms.
Bailing out the airlines means we all split the cost of keeping those people employed.
Failing to bail them out means the owners get what they deserve, but the employees get fired and there's nobody willing to hire them.
You are suggesting tough love. I get that. There's no perfect answer here. I'm leaning heavily in favor of the bailout, paid now and repaid by the reversal of the tax cut for the rich or other actions (such as "hey, time for you guys to repatriate all that money Trump said you would, and hand it over").