I have a rectangular leather ammo pouch with a top lid that holds 20 cartridges. It is worn on a belt always on the outside of all my clothing in the front and is easily accessible. When I start the hunt. I load from the 20 cartridges whatever it takes to fill my rifle capacity. The rest are staggered in the pouch making room for my large fingers to easily grasp extra rounds, especially when dexterity or frozen fingers don't operate easily. The leather pouch dampens noise, removes reflection and insulates from extreme weather and pressure spikes. Especially in hot weather when the sun heats up the cartridges causing case sticking and bullet flight unwanted changes. The buttoned flap is extra security.
I don't like the open type elastic cartridge holders that slide into the rear of the stock. In Idaho a friend was dragging a deer downhill to a road and when he got there, the 7 cartridges he had in it were missing. Obviously fell while navigating through brush. When he got to the dirt road he began to hear wolf calls around him but did not see them. The hair stood at the back of his neck which made him check his weapon and that's when he discovered the ammo lost. He had left his pistol back in camp trying to save weight. He had 2 loaded cartridges in his rifle.
Every body is free to make their own choices. If you hunt ranches, stands, guided hunts... you can get away easily with just a loaded rifle. If you hunt wilderness, predator country, it's prudent to be cautious.
If hunting deep wilderness via float trip, plane or horse back, I carry an extra 20 cartridges in a waterproof container and it stays in camp. If I have a partner and is using the same caliber, then I only carry an extra 10 cartridges in the emergency box in camp.
I also carry a 329 44 in a chest holster with 12 extra cartridges.
I guess the scout motto is worth living by, at least for me.
