title_body: Are some beers meant to be served flat?
upvoted_answer: Traditional ale styles of beer were only carbonated by using natural yeast and remaining sugars post fermentation. The ale house would "pull" pints from huge wood tanks, generally located below their taps by using traditional cask systems. CO2 was not available to breweries for most of the worlds brewing history. This led to a ale that was cellar temperature and with little to no carbonation. 
  
  Today breweries try to replicate this process by "cask conditioning" carbonating naturally their beers. So, there is no forced carbonation with CO2 and generally they do not refrigerate cask ales either.