Why are dichotomous keys so hard to do.

A dichotomous key is a sequence of methods which allows the identification of a living thing.  This key will consist of a series of options or choices that lead the user to the right name of a given item. This is so hard to do because it involves the six taxa. You also need to gather all the significant details and characteristics of the specimen. What makes it harder is the fact that living things are always variable so you need not to rely on a single observation.