Most likely because if you are doing ML and do not have a PhD (or previous experience), you are just looking at calling a library function that you do not understand. The majority of 'machine learning meetups' (not in the Bay Area), are attended by programmers that are looking to figure out how to call an R package to give them recommendations or similar items in a list (clustering).

edit I just read the other replies to this post. I believe that most startups with Machine Learning teams are doing more than just calling R-libraries; most development work that I've done for myself and teams has been for tooling and operationalizing data infrastructure (i.e. data engineering, not data science). However if you need a simple recommendation for an app then calling the library methods without 100% understanding may be enough (but calling library methods without underlying understanding is a bad trait in a programmer (e.g. calling the sort() function without understanding quicksort)).