Why do biological classification keys always present only two choice at each step?

BTW I am doing a shark dichotomous key analysis

The biological classification keys always present only two choices at each step because; it is simple, more efficient way of separating organism, without confusion.

Biological classification is the process in which scientists group living organisms based on their similarities and differences. Originally similarity was determined by examining the physical characteristics of an organism but modern classification uses a variety of techniques including genetic analysis.