The length of time between cycles where the transformer is charging the iron core decreases with the increased frequency.
Imagine trying to move a baseball 1Hz between your hands, then try it 1000x faster... it might be possible with a smaller ball, but its still difficult.
I has to do with the amount of magnetic flux that is being stored into the metal in the transformer core. The faster the switching, the less time it has to discharge/charge and therefore the correct device will account for this.
airplanes use 440hz transformers and 440hz AC for most systems, since they are smaller/lighter and weight is an issue in airplanes.