The Dunning Kruger effect is a cognitive bias, affecting people at all levels of intelligence, where people tend to overestimate their knowledge or ability in specific areas, especially new ones for them. A lack of self-awareness is considered a reason for this effect because it can prevent people from accurately assessing their own ability/knowledge. Because confidence is so highly praised and sought after in many cultures, many would rather pretend they are skilled or knowledgeable to avoid appearing inadequate or losing face.
Citation: Kruger, J., & Dunning, D. (1999). Unskilled and unaware of it: How difficulties in recognizing one’s own incompetence lead to inflated self-assessments. Journal of Personality and Social Psychology, 77(6), 1121–1134. https://doi.org/10.1037/0022-3514.77.6.1121