Is it still important for web pages to have blue and underlined links? Does it help click rates?

Some of the larger sites like walmart, yahoo, google, amazon, and ebay continue with the blue and usually underlines links. Most graphic designs stay away from the look. I have to ume that the large companies have paid good money for usability and have a proven record to show that the standard blue underlines makes them more money than if they changes to other colors.