For re-writing URLs to generate SEO friendly pretty URLs, it was usually recommended to use the ending extension (normally .html), as without the extension, the URL seems to be incomplete. Probably, because a webpage should be similar to a file (as actually is) rather than folder. And it was the method used by almost all websites.
However, I have been recently noticed that major content websites have removed the html extension from the end of URL. This is the case of stackexchange projects too.
Is it beneficial to remove the html extension? Or it has been convinced that it is useless and it is prettier to have URL without extension?