Because they fail at life on every conceivable level and then make up even more levels to be oppressed on?
….The first question that needs answering is why liberals would need to increase their self-esteem in a way that conservatives do not. The answer is simple: liberals have less self esteem than conservatives to begin with. This is the conclusion of a 2012 paper published in the Journal of Research on Personality. The paper included two studies that found that liberals had lower self esteem than conservatives. The first study’s sample was moderate in size and consisted of college students. The second study made use of decades of data from the General Social Survey. The GSS is a large and highly representative survey that has been administered in the United States for over 40 years. Another paper published in 2014 replicated this finding in two more samples. Thus, the finding that liberals have low self esteem has been replicated several times, including one replication with an extremely high quality sample….
I mean this article.