Why are BE pistol range boxes tapered?

Probably a dumb questions but why are most commercial pistol range boxes tapered? i.e. Wider at the bottom and narrower at the top? Why is the lid or front cover tapered as well? I suppose I am missing the obvious so please enlighten me.

It gives the lid more stability when it is open with a spotting scope hanging off of it.  Also gives you a surface to clamp the lid to the box.

IMO the answer is cause its a design that works, there have been many type gun box styles over the last 60 + years the ones that worked are what the few companies today that build gun boxes use, the others fell to the way side.

You must live where the wind it wimpy.

Stability is the goal, as stated above.