I usually tell my students that it's used to make the root we use most often easier to write. It's also the lowest root and, in math, we often use don't use a symbol for the lowest one. We don't use an exponent of 1 on an x, nor do we use a 1 for a coefficient. I usually have them put the 1, or 2, in when they are working the problem to help them and then have them rewrite the answer without the 1 or 2 so that they get used to "standard practice" I don't hesitate to have beginning students use the numbers.
Mary Liz Pierce Math Instructor Central Arizona College Superstition Mountain Campus