Unlike a car, a plane at cruising altitude doesn't immediately crash into the one in front if the pilot doesn't pay attention for half a second, and despite their far higher absolute speed, actions performed when flying have a much lower relative speed.

For example, in a car, several seconds of following distance is normal and following another car that closely is common. In a plane, which can move in 3 dimensions, horizontal separation is measured in minutes and it's not that common to be following immediately behind another plane at the same speed: https://en.wikipedia.org/wiki/Separation_(aeronautics)#Horiz...

In cruise, it's extremely rare to be within 3 miles of another aircraft laterally and 1000' vertically.

Takeoff, initial climb, descent, and approach to landing are high workload times, easily holding the attention of the crew.

Cruise is much more relaxed and much less need for hair-trigger responses. My aircraft has audio and visual cues if an aircraft breeches a 2nm (or thereabouts) and is within 1000' vertically. Other than that, it's systems monitoring, weather monitoring, keeping up on the nav progress vs fuel remaining, and making sure the automation isn't trying to kill you, either subtly or acutely.

There are lots of differences, but one is that situations requiring aircraft pilot intervention often have a timeline measured in minutes. The recommended procedure for handling an emergency situation is to pull the checklist for that situation before starting to ensure you don't miss anything. Even urgent situations, like a TCAS alert, will often give 30 seconds warning. By contrast, this driver had roughly 2 seconds to notice that the autopilot was silently failing to handle the situation and to apply the brakes to prevent a collision.

Extensive training, restriction of hours worked, health restrictions (pretty sure my ADHD would prevent me from being a commercial pilot)...

Also, my understanding is that aircraft autopilot systems are designed to allow for pilot response to take up to three seconds. Three seconds on the highway is a lifetime.

Car driving also has health preconditions.

Airplanes are 10km up when cruising. Almost any error a pilot makes has minutes of time to be corrected. Contrast with 1 second while driving. Take off and landing are far more involved and take 15 minutes each (approx).

Aircraft on most kinds autopilots crash into mountains without any intervention. They are mostly completely blind.

They take shifts.

I've flown "right seat" (not pilot) a fair number of times. Air traffic control interacts with the pilot quite often and at fairly unpredictable times. This requires the pilot to be alert and respond promptly to a request or direction from air traffic control. If the pilot doesn't respond promptly, air traffic control repeats the request with more urgency and goes into the "lost communications" procedure if there is no response.

tl;dr: aircraft pilots generally must be attentive. Tesla drivers on "auto pilot" - not so much.