[matthewkayin]

There are plenty of stories of ATC helping to guide pilots back to the ground after an engine failure or after a student pilot had their instructor pass out on them or something like that.

Even if most of the work is routine, you definitely still want a human in the loop.

[jrockway]

It's worth pointing out that plenty of pilots take off and land safely at uncontrolled airports. ATC is a throughput optimization; the finite amount of airspace can have more aircraft movements if the movements are centrally coordinated. It feels like we are nearing the breaking point of this optimization, however, and it's probably worth looking for something better (or saying no to scheduling more flights).

[nradov]

The FAA already does issue temporary ground stops for IFR flights when ATC capacity is saturated. This acts as a limit on airlines scheduling more flights, although the feedback loops are long and not always effective. The FAA NextGen system should improve this somewhat.

https://www.faa.gov/nextgen