Typically when getting a new column they come with rubber septums on the end of the capillary column. This can introduce unwanted contaminants into the front end of the column. By removing approximately an inch , this will help eliminate the possibility of introducing these contaminants during an analysis.

I agree with what spiax said. Also, I never trust a cut someone else did, it could be suboptimal. Also, after the cut is made, the chemist could have jammed the end of the column up against the bottom of the jet, which can chip the end of the column.