Speaking only from personal experience on DG hunts, the "need" for a double is far over stated, today. Consider that there will be an armed PH, and likely an armed Game Officer, and possibly an armed property owner and maybe and armed tracker. In my case none of that meant I didnt want a Double Rifle, nor did I fail to bring a Double Rifle and even so I only fired ONE shot. I actually fired more shots to confirm I would be on target than on the hunt.

Might I have needed a quick second shot, sure; but with three other guns present (doubles and bolt guns); I suspect that I could have gotten a fast reload with something like a Ruger No.1 or Martini