title_body: Why do steins have lids?
upvoted_answer: Today they're largely just traditional.  However, originally they helped:
  
  
  To keep the beer cool by preventing airflow from above.
  To keep insects and other contaminants out.
  To prevent spillage while cheers-ing and generally carousing.
  
  
  See the following article on Stein Lids for more detail.