Because they can weigh things by eye man.
I don't know but that reminds me of a similar joke my uncle used to tell...
Mascarpone
He was turning things over in his mind.
Jar Jars.
On a scale from one to ten, urinate.
Because they all had a tare
A skeleTon
Somewhere over the rainbow weigh a pie. (sounds like way up high)
He had a fear of eights