meaning of A slice off a cut loaf is never missed

A slice off a cut loaf is never missed meaning in Idioms Dictionary

applied colloquially to describe having intercourse with an individual who is not a virgin, particularly when these are generally in a relationship. The example means a loaf of loaves of bread; it is really not easily apparent, after the end has been eliminated, just how many cuts have been taken.('You never ever miss a slice from a cut loaf' normally used.)