oops sorry about the 2 posts in a row, it said the first one didn't work... I guess it did. You adjust it just cause of personal prefference, some people like the strings really low, some don't. Sometimes when you buy a guitar new the store sets it up really badly so you usualy have to adjust the truss rod on a new guitar unless you pay the store to do it, and over time the neck will change a bit depending on tempurature and humidity.