<i>A question that has never been answered on this blog is why do political scientists need to know quantitative methods?</i>
Same reason why anyone needs to know quantitative methods. When the number of observations in a study is higher than, say, 10 or so, relationships among variables are impossible to understand without using quantitative methods.
For example, what is the relationship between GDP and democracy? Qualitative methods are of very limited utility for answering this question.