Commercial aviation is a little different in that on an IFR flight plan (which encompasses pretty much the whole time the autopilot is active), ATC is maintaini

Commercial aviation is a little different in that on an IFR flight plan (which encompasses pretty much the whole time the autopilot is active), ATC is maintaining a 3 mile lateral bubble around the aircraft, making sure that there are no conflicts. So even though the pilot may not be as engaged in see-and-avoid behavior (which is the primary responsibility during VFR), there should be no risk of mid-air collision. Aviation practices are very much about ensuring that there are extra layers of protection that should all prevent an accident, that even if one fails the others continue to maintain safety. ATC, autopilot, pilot, TCAS, etc. Contrast this with automotive practices, which seem to be about achieving the minimum amount of safety possible.