Google makes their own computer servers typically because they need customized server for their own needs.
According to Wikipedia: Google Platform;
Though the numbers are not publicly known, some people estimate that Google maintains over 450,000 servers, arranged in racks located in clusters in cities around the world, with major centers in Mountain View, California; Council Bluffs, Iowa; Herndon, Virginia; Lenoir, North Carolina; Atlanta, Georgia; Dublin, Ireland; Saint-Ghislain, Belgium; Zürich, Switzerland; Tokyo, Japan; Beijing, China; …Racks are custom-made and contain 40 to 80 servers…
Servers are commodity-class x86 PCs running customized versions of Linux. The goal is to purchase CPU generations that offer the best performance per dollar, not absolute performance. Estimates of the power required for over 450,000 servers range upwards of 20 megawatts, which cost on the order of US$2 million per month in electricity charges.
Take a tour to Google Datacenter: