First, let me say that I never try to convince people to change what they are doing. All I can do is explain what I do and why. And, I'm always open to new ideas. Evolution is a good thing. ::
I carry my bag and horn separate for several reasons. I like the horn tucked up under my arm. I find this to be the most "out of the way" position. The measure is attached to the horn. (It couldn't be any more convenient) If I carry the horn "over" the bag, it prevents easy access to the bag and sticks out too far. Too bulky. The bag sits just under the horn (touching it).
Because the horn and bag are carried high, under the arm, they don't flop around if I have to get someplace in a hurry. Admittedly this is not important if you're standing on the rifle range.
I also don't want the bag attached to the bag for convenience sake. If I have to loan my horn to someone, or fill it with powder, I don't want to have to take the bag off and drag the bag around with it.
There are as many ways to carry your horn as there are horns. I've seen people carry their bag and horn on opposite sides. It works for them.
I agree about the patch knife, etc. It seems incredible to me that the mountain men had so much junk hanging on the straps.
Let's face it, modern man likes gadgets. I think we have added many "specialized" items that the old-timers did without. They could butcher a deer, slice bread, carve a ham or cut a patch, all with the same knife. It seems that we've lost that ability. I think many of the items attached to the modern mountain man's "utility belt" are undocumented and unnecessary.
:imo: