It is more about the approach that keeps them there. i quote-
"Part of what makes Google such an amazing engine of innovation is their internal technology stack: a set of powerful proprietary technologies that makes it easy for Google developers to generate and process enormous quantities of data. According to a senior Microsoft developer who moved to Google, Googlers work and think at a higher level of abstraction than do developers at many other companies, including Microsoft: “Google uses Bayesian filtering the way Microsoft uses the if statement”
Also Google's publications tend to run 3-4 years behind when the technology is actually developed. So this is actually describing the Google stack as it existed c. 2004.
