In this pace world everyone needs everything at a tremendous pace, as like other things people want website’s also to load at lightening speed.
Suppose you want to do urgent search and on search result you clicked a website whose loading time is very high, will you wait the website to load or will you exit? The answer is yes I will exit. Instead of wasting my time watching a loader of a website or half loaded website, I will go to another website
Google wants to give an immense feeling to their user. For that very reason, in April 2010, Google started to take load time into account when ranking sites.
Here is an infographic from Quicksprout which explains How load time affects your website rankings.