The answer is: The United Farm Workers were looking for long-term changes in labor policy rather than short-term gains.
National Association for the Advancement of Colored People made their move when there is a report regarding discrimination/unfairness based on races or ethnicity. Even though they helped a lot of people from their activities, it only provide short-term gains.
The united states farm workers focused their efforts on electing the representatives that can reconstruct the economic system. Such changes would impacted american labors in the long term.