Unless you really mess-up badly, chances are you would run-out VERY close to your destination so, theoretically, the tow should be very short.
You point out a very good point about theory versus reality. No one's going to make a 100 miles trip with only 80 miles worth of charge and be stranded 20 miles out. If anyone runs out of charge, it will always be near their destination or at a destination where the charger's not functioning. It does add to your point that the tow-anxiety is way overblown.