and anyway I don't see drivers being comfortable driving on a dashed line;
Well that's partly the point. You aren't supposed to be comfortable. You are supposed to be alert when you are in them because you are either being passed by someone or doing the passing yourself.
Any other time you are expected to be between the lines in the center.
I guarantee when you see someone coming toward you at a high rate of speed, you won't have an issue with how comfortable you feel about having part of your car over those dotted lines hugging the edge.