When did it become legal...

I've noticed lately while driving, people are willing to cross a double yellow line to make a left hand turn. I've been wondering two things. One - when did it become legal to cross a double yellow line? Two - is this a continued sign of our society's laziness? I'm not sure I have an answer to either. But I don't understand why people don't bother to drive a few more feet and make a legal turn.