Perhaps driving instruction has gotten better than when you were instructed? I could be long, and I'm not googling it first, but if I recall correctly, you are not to enter an intersection unless you can immediately exit the intersection. I.e., you can't go into the intersection unless you can keep going. I completely agree that it's impractical if you're making a left hand turn though - it could result in an impossibility for some lanes to ever make a left without running a yellow/red light, else cutting someone off at certain times of the day.
Remember though, 3 rights make a left.