"On a machete, a wrist loop reduces the grip you need on the handle so you can chop longer before tiring, like the webbing on cross country ski poles."

I read about this in Don Paul's "Everybody's Knife Bible"
The right length wrist lanyard lets you hold the end of the handle between thumb and two fingers and extends the radius of the blade when swinging it in a chopping motion. The knife still needs some weight in the blade for this to work but it does seem to help. (on my Ontario Spec-Plus Pilot Survival knife which I carry for backpacking/dayhikeng)

Unimogbert