in its results page, Google bolds the words of the query, so if the URL contains, they will be in bold, which will attract a little more attention to the Internet
users who look at the URL of each result before you click can better assess if the page meets their demands
URLs with well-chosen word will be easier to remember and understand when they are sent via email, Twitter, etc..
the best for the end: those who will take your URL into a link will make you a good link optimized since the clickable text contain words strategic (provided that words are separated by separators good). It is 90% for this reason that it is efficient to have keywords in the URL.