Nuclear war could happen very quickly - a matter of hours. Civilian & commercial aviation might not be safe or even allowed. Driving from Orlando to Kansas could be a nightmare of limited fuel, martial law, & dangerously desperate people along the way.
Natural disasters aren't much different. If Yellowstone explodes tomorrow, there is little chance Allen will get to Kansas. That would NOT be the direction to head for safety. If a 200 ft. tsunami is headed for Florida, flying away is probably the only way to save yourself & family, yet Allen may have to wait in line to take off at any airport. The ground crews & air traffic controllers might have ideas of escape themselves, so he can't count on them to ready his escape plane.
Then there is the dilemma of WHEN to head to safety. Back when we had hurricanes, I faced this problem numerous times. If you leave too late, traffic & circumstances could foil your plan. If you leave too early, you leave your property to the thieves & you risk wasting time & money on what turned out to be nothing. The urge to wait a while longer is great. So is the urge to stay put & ride out the storm.
Mass panic has a way of spoiling the best of plans. Traveling 1400 miles to safety doesn't seem like such a good plan.
“Everyone has a plan ‘till they get punched in the mouth.” - Mike Tyson