As if everyone employed at google is a core search engineer. Moreover, if you take your average programmer and let him/her implement an array at a low level, you’ll get either a mess or nothing, since the complexity of using arrays and btrees has nothing to do with the complexity of implementing these. And the complexity not in theory knowledge, but in an implementation itself. One basically cannot write, test and prove it in short term (see e.g. “Implementation Issues” on wp).