I suspect that's much like Hollywood, i.e. why if you're an actor you want a gross point (a share of the revenue) and not a net point (a share of the profit, which on paper won't exist, for tax purposes).
Because the companies are poorly run. This has little to do with the industry itself and air travel is clearly not going to stop anytime soon. Some companies may die, but again aviation is not a 0 profit industry, these are just shitty companies who grew beyond what they could manage.
Some airlines are profitable, Southwestern, Ryanair, Easyjet, Westjet - but this is offset by national airlines which aren't.
US airlines are never profitable because the more money they lose apparently the more willing people are to bail them out