Sometimes you have reason to hide the points of your object. Maybe you’re making changes to your stroke width, maybe you’re adding a subtle effect, maybe you just find the selection color to be distracting.
The bounding box is the part of the move tool (V, the black arrow) that allows you to resize your entire object as opposed to one point at a time. It can get turned off by mistake sometimes leaving you wondering why you can’t resize objects.
I use it for die lines and for margins among other things. You’ll find uses for it. I use it often enough that I’ve given it a keyboard shortcut.