Nikhil Garg outlines 7 reasons why Quora chose to build their own machine learning platform rather than buy an existing one. He explains that no commercial platform can provide all the capabilities they need, including building end-to-end online production systems, integrating ML experimentation and production, openly using open source algorithms, addressing Quora's specific business needs, and ensuring ML is central to Quora's strategic focus and competitive advantage. He concludes that any company doing serious ML work needs to build an internal platform to sustain innovation at scale.