Did you ever look at a box of shotgun cartridges?
They list the length of the cartridge, the guage, the weight of the shot, the size of the shot and the drams equivalent of powder.
Like anyone really pays any attention to that?
Or how about the old "buffalo hunter" cartridges? They listed the same data....2-1/2"-45-70-400-1330 Sharps.
Today you walk into your favorite shop and grab a box of .45-70 cartridges...
In the "olden days" you parked your horse at the rail, hobbled into the general store and on the shelf you saw the following...
2.105"-.45-70-300-1880-45 Government
2.105"-.45-70-330-1780-45 Government
2.105"-.45-70-350-1560-45 Government
2.105"-.45-70-405-1330-45 Government
2.105"-.45-70-500-1200-45 Government
And right on the shelf next to those there would be the appropriate number of boxes of 45-60 Peabody (Sporting),44-60 Winchester, 44-60 Peabody (Creedmoor), 45-60 Winchester, 45-70 Winchester (Centennial), 45-100 Ballard, 45-125 Winchester, 45 Express, 45-70 Van Choate, 45-70 Sharps (Straight), 45-70 Sharps 2-1/10", 45-100 Remington (Necked), 45-82 Winchester, 45-85 Winchester, 45-90 Winchester, 45-90 Winchester (High Velocity), 45-90 Sharps (Straight), 45-100 Sharps )(Straight), 45-110 Sharps (Straight), 45-110 Sharps (Special)...and the list goes on and on!
Besides all that stuff, like an earlier poster mentioned, every lot of factory ammo is loaded differently. Different powder, different bullet, etc. (and some of the stuff the factories slap on the market contain components that you can't buy for reloading).
K.I.S.S.