Final answer:
People may express prejudice because it helps them maintain a positive self-concept and protect their in-groups by blaming out-groups.
Step-by-step explanation:
The main reason why people who feel relatively gratified versus relatively deprived may express prejudice is because they want to maintain a positive self-concept and feel good about themselves. Prejudice helps us protect our in-groups, which are the groups that we identify with or belong to. When we blame an out-group for our frustrations or blocked goals, it helps us maintain a positive view of ourselves and justify our success.