On my first backpack trip, I just knew I would need my machete, so I had it lashed on my pack. It fell off several miles into the hike, on a popular part of the trail, un-noticed.
When my pal and I hiked out, I found the machete where it dropped in the middle of the trail, covered with muddy bootprints...it had laid there four days and been stepped on a bunch.
I never needed it on that trip, and I never carried it again. Still have it, though...good for trimming hedges around the house.