Cut part of your arrow from the nock end? I have seen a few people say this and I was wondering why?

The endsare where you get most of your inconsistancies in a shaft. Arrow straightness is measured over a 28" span. Guess where they measure that 28 inches? in the middle of the shaft.

It also can make it easier to make a spine adjustment on a carbon arrow since you don't have to worry about the insert.

Rifle barrels are that way too. A new barrel blank needs to have at least 1" cut off of each end to get rid of run out that occurs in the manufacturing process.