Research in social psychology is a complex endeavor that requires a set of skills in order to be able to produce quality output, two of the most critical skills being social and cultural competencies.
Social competence is defined as “the ability to handle social interactions effectively” with all it entails, a wide array of cognitive, emotional, behavioral skills, awareness of the social context and of cultural and personal values involved on interpersonal relationships, while cultural competence can be defined as “awareness of unique, and defining characteristics of the populations”  and relates with understanding the importance the social and cultural influences have on the individuals we’re working with.
The kind of awareness that social and cultural competency brings is of vital importance on social psychology, given how it deals with how people’s behaviors can be influenced by others it implies high social competency as a prerequisite if we wish to accurately measure the impact of such influence, while cultural competence is also needed because interpersonal relationships in the modern world happen in diverse, heterogeneous populations and without this awareness, the accuracy of the research done is also badly affected.
We can see the importance of these competencies if we focus on a specific concept such as the fundamental attribution error, or the tendency to over emphasize personality based behavioral explanations over situational ones. When doing research on this concept, we need to be fully aware of the way the interactions developed in order to be able to spot when the cognitive bias arises and why, and we cannot do so if we lack the social and cultural nuance to understand whether a person is judging another because of the situation or because of who the person is.
For this particular concept, differences have been perceived in the degree of bias across different cultures, a factor that without cultural competence we might overlook and something which would greatly hurt our research, and as cultural values might become part of the judgement a person makes of another based on personality instead of situation, without a finely tuned cultural competence skill the research done is nearly guaranteed to stray towards unproductive paths that fail to reveal the possible causes of the cognitive bias.
A relevant example related to this bias can be seen in the way foreigners are perceived as a threat and associated with bad traits to some Americans, a topic that with recent events has gained importance and interest for the country. Research on this topic would ignore quite a few variables on the complex issue of what causes a person to distrust another based on a specific trait, if we just take the isolated scenarios and ignore the cultural factors involved that ignite such behavior, such as the influence of personal experiences, recent events in the country and the community or the priority of the values held in the environment the scenario develops. If we ignore the perspectives of the individuals involved, we might as well fall in the same trap we are attempting to study objectively.
In conclusion, social and cultural competences are vital parts of social psychology, because the topics it deals are tightly related with the need to be skilled on these aspects to produce quality and accurate research


Sources

Cultural Competence in research
https://catalyst.harvard.edu/pdf/diversity/CCR-annotated-bibliography-10-12-10ver2-FINAL.pdf
Social Competence
https://onlinelibrary.wiley.com/doi/abs/10.1002/9780470479216.corpsy0887
Fundamental Attribution error