Title.
Elefront gets it right. This way you can easily control and change baking layer. Specially useful when baking many different things on different layers in random order, often this can’t be easily systematized so using layer attributes is very cumbersome in this case.
Are you aware of the bake selected shortcut?
Which one do you mean? 
I’m using this shortcut to bake to the current layer for quick drafting. As you can see on the screenshot, I set it to ‘Insert’. A key which I think doesn’t really have much use in Rhino
