It is important to avoid generalizations and assumptions about people's behaviors, as each individual's actions are influenced by their unique experiences, values, and circumstances. It is not accurate to make a sweeping statement that guys cheat on pretty girls with "ugly" girls or vice versa, as attractiveness is subjective and varies from person to person.
Infidelity or cheating in a relationship can stem from various underlying reasons, including emotional dissatisfaction, lack of communication, personal insecurities, commitment issues, or even seeking novelty and excitement outside the relationship. Cheating behavior is not limited to any specific group of people, and it can occur in relationships regardless of the physical appearance of the individuals involved.
It is essential to remember that physical appearance is just one aspect of a person, and a successful and fulfilling relationship involves much more than superficial factors. Trust, communication, emotional connection, and shared values are crucial elements that contribute to a healthy and stable relationship.