That is probably dictated by Google. Google won't rank posts with a lower word count.

You find that evolution especially in blogs. From min. 250 words pre-2010, it then went up to 350-400 words minimum. Since 2012/2013 it is estimated to be at least 450 words required, most sites targeting min. 550 for "newsy content" articles and 700+ for everything else.

For so-called cornerstone content, the longer the better. A friend of mine ghostwrites high quality referential articles and +3k words is usually minimum for those. The only aim of that content is to rank in Google for topical queries. And, you bet, those articles read good and achieve long on-site time.