You know, about 5 years before anyone ever heard of a Witcher game, I carried a great sword around with me at Renaissance Fairs. I did not have it sheathed on my hip, but instead hung on hooks that were attached to a harness right at the base of my neck. Why? Because I'm 5'11" tall, and the sword, from tip to pommel, was just over 6' long. If you looked at it from a medium distance, where you couldn't see the hooks, it looked like it was floating behind me, instead of hanging on the hooks. It didn't have a sheath, I was a poor bard, not a fancy noble. I was lucky I could afford the sword.
Nice story! But let's say you could afford a scabbard for your 6' sword...that would be a 5' scabbard, right? How would you draw the weapon without looking silly?
I stand to be corrected, but I don't think they made scabbards for swords with 5' blades, at least not on a regular bases.
But besides that, a great sword swung on the back for transportation does make sense. Or carried in some other way, such as: