Answer: occurrs because of the REPRESENTATIVENESS HEURISTIC.
Explanation: Representativeness heuristic can be defined as the act of making conclusions under probability or uncertainty. Here conclusions are made based on representativeness which makes the conclusion less accurate because the fact that some is a representative doesn't make it a likely outcome.
It is an approach that employs a practical method not guaranteed to be optimal or perfect; not following or derived from any theory.
An example can be seen in the use of horoscopes.