Why are most ammo holders seen in Africa open top style?

[CBeck]

I have a couple versions….elastic open top and bottom and leather with closed bottom.

All leather…..

 

[BGGMKLR]

What is the reason most ammo holders on the belt are open top instead of one with flap closure? Is this a legacy of double rifles needing quick access to more ammo that has just continued with more modern rifles holding 4 or more rounds? Is there a real functional purpose to avoid a flap closure on a belt mounted ammo pouch for use in Africa?
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Good points all. I believe the decision is just a matter of personal choice and what works effectively for YOU.
Personally, I settled many years ago on what I consider the best of both worlds...security... and ready unhindered access.
My ammo pouch is the belt worn, suede, bi-fold variety. It is snapped closed 90% of the time, unsnapped and dropped open as circumstances dictate. No top flap to hinder access in critical moments.
Best
Spike