6 pounds isn't terribly heavy for an 85 L full frame pack.

People pay quite a premium for a 4 pound reduction in weight. When your base weight is around 10 pounds you're talking a 40% reduction in weight!

You are probably starting at a heavier weight where the % reduction isn't as great. One thing I have noticed is with big bags people tend to take more stuff. With a smaller bag you run out of room sooner and are forced to scrutinize what you are bringing. That reduction in weight can be significant!