The short answer to this question is that knowing about racial and ethnic development helps to foster a sense of empathy across different cultures. According to proponents of critical race studies, one of the major goals of a multicultural movement is solidarity and understanding. As such, concepts such as "speaking my truth" or "testimonios" are generally encouraged by proponents of race and multicultural studies. Both concepts (speaking my truth and testimonios) amount to individuals sharing their racialized experiences in the world, explaining how they perceive race and ethnicity as factoring into their everyday experiences. The more an individual has been able to reflect upon his or her development of an ethnic identity, the more that person may be able to share stories and experiences that help them to express themselves across multicultural borders.
Alternatively, even if we do not feel that we have specific stories to tell, the awareness of the idea that racial and ethnic identities exist helps us to understand that not all perspectives are the same. By recognizing and treating racial/ethnic identity as a fact, we also recognize the potential for individuals to develop identity in various ways, including culturally. By understanding racial/ethnic identity, we understand the broader picture of multicultural studies, which is a celebration of differences, experiences, and ways of being in the world.