Rocket recommends doing DS&A interviews in Python instead of JavaScript because the concise and English-like nature of Python syntax may enable more efficient use of time in a time-pressured interview setting. This is why Python is the most popular language for solving DS&A problems. In addition, Python is the most popular language for data-related work, e.g. data analytics or data science, thus it will be in students' favour to learn Python in addition to JavaScript.