According to music industry resource Mix magazine, in-ear monitors come in models that can be formed exactly to the performer's ear. When an in-ear monitor is formed to the ear, it can more effectively block out all other sounds. This allows the mix to be heard easier by the performer, and it also allows the volume of the mix to be lowered, which reduces damage to the performer's hearing.
Audio resource Learn Church Sound mentions that in-ear monitor systems, because of their significantly smaller size when compared to monitor speakers, are much more portable. An in-ear monitor system can fit in a bag and be easily transported from one show to the next.
According to Johnson Audio Works, in-ear monitors significantly reduce the stage volume because monitor mixes are no longer put through large stage speakers. When the stage volume of the monitors is eliminated, this allows a better mix among the instruments on stage. A lower stage volume also means that there is not significant sound bleeding from one microphone to the other. Sound bleeding means that the sound of the guitar amplifier, for example, is being picked up by the vocal microphone. When the stage volume is lower, the guitar amplifier on stage can be lowered and it will not bleed over into other microphones.
A loud monitor mix coming through speakers on the stage can sometimes be heard by the audience. If the monitor mix is too loud it could start to affect how the main speakers are heard by the audience. With in-ear monitors, the monitor mix is eliminated and the audience only hears what was meant to be heard through the main speakers.