why do people tend to ignore the importance of Multicultural Psychology ?

Answer 1

That's a pretty broad statement. What evidence do you have that "people" ignore the importance of multicultural psychology?

Those who do ignore this probably do so out of ignorance or perhaps distrust of people who are different. Check this site.

http://findarticles.com/p/articles/mi_m0825/is_4_71/ai_n15970797/

Answer 2

Much of this is linked to prejudice, especially the factor of ethnocentrism.

http://www.members.cox.net/dagershaw/lol/PrejudiceChanges.html
http://www.members.cox.net/dagershaw/lol/Prejudice.html
http://www.members.cox.net/dagershaw/lol/PrejudiceCauseSolution.html
http://www.members.cox.net/dagershaw/lol/PrejudiceUsThem.html