Siri is behind, and Apple (NASDAQ: AAPL) presumably knows it. On the flip side, Amazon.com's (NASDAQ: AMZN) Alexa has emerged as the leader of the virtual assistant pack, thanks largely to its massive catalog of third-party Skills, of which there are now over 13,000.Apple first opened its engineering office in Seattle back in 2014 after acquiring Union Bay Networks, and it has been steadily expanding its presence in Amazon's backyard.