> The carriers need to eat the costs of forcing too much demand on ATCs.

Running ATC (and limiting flights if necessary) seems like the job of the government to me.

Why put this on the carriers?

You are correct. Robustness requires a system that is working within it's tolerance margin, and stressing that inevitably leads to failure. A fault-tolerant system in this case would require a large amount of redundant humans. Unfortunately, the capitalist mindset prevents accepting any amount of "waste" as tolerable, which makes a robust system impossible to implement over time. Every system touched by a capitalist optimizer will eventually fail.

The idea that waste must be reduced is killing society, and this mindset must be addressed first before any other safety-critical system can be made reliable again.