I agree -- bike boxes are quite miraculous. They're the one instance where paint actually is infrastructure, and I use them any time I can just to show other cyclists that they are allowed to.
But to add some nuance to the argument: bike boxes are an improvement over filtering up on the side of the road. Doing what (I assume) GP did and taking the lane behind waiting cars is about as safe, because any other cars coming up from behind ought to see you as they roll up to you, being that you are in front of them and not to the side. (And they're already paying forward attention thanks to the car ahead of you.)
That's true. There are too many different cases, that's why I am saying common sense. If there is a bike box, go ahead and use it. If there is none, then be prepared to not be seen by the car. Traffic is just complex.
PS: In my experience, if there is a bike box, then there is also often a separate bike lane. I was mainly speaking about roads where there is no real bike lane. If there is one, then most things just work out fine.
But to add some nuance to the argument: bike boxes are an improvement over filtering up on the side of the road. Doing what (I assume) GP did and taking the lane behind waiting cars is about as safe, because any other cars coming up from behind ought to see you as they roll up to you, being that you are in front of them and not to the side. (And they're already paying forward attention thanks to the car ahead of you.)