One of the most important delays is webservers is getting your query to the webserver, and the response back. THis latency is bound by the speed of light, which even Google has to obey. However, they have datacenters all over the world. As a result, the average distance to any one of them is lower. This keeps the latency down. Sure, the difference is measured in milliseconds, but it matters if the response has to arrive within 1000 milliseconds.
