Continuous effort to offer better user experience is what makes Google different from others. And that is the reason, Google is putting so much stress on website loading time. How much time your website takes to load is a factor Google is likely to consider to rank your website!
Just think: a user runs a Google search, Google displays the results, and then when the user clicks on a link, it takes several minutes to load the page! Why should Google list such a web page that annoys its user? Logical!