What are the reasons of racial discrimination in the US?

Answer: The reasons are many and varied, but a few are discrimination which includes the belief that the conduct is NOT discriminatory, or that discrimination favoring a formerly out-group is OK. Almost all employment discrimination found by EEOC or courts is "technical" "statistical" and other unintentional discrimination. No fear or entitlement was involved, just accidental outcomes from well intentioned conduct or policies. Actual discrimination is rare.

Answer: Some other reasons would include an actual feeling of entitlement for their race on the discriminator's part, viewing others races in a stereotypical manner, being afraid of what's differentand/or new to oneself, feeling slighted by another race, feeling superior and thinking the discrimination is more natural than what it is, and so on.