Column widths are standardized in print, magazine, and books for a reason: to minimize eye movement required. The larger that web screens get, the broader the column lengths often are, which forces more eye movement, which causes eye strain, which requires vision interruption, which impedes reading comprehension.
Smart phones are great for short articles because the screens are roughly the width of a newspaper column. It forces the text into an appropriate width, rather than expanding to fit the available monitor space like many websites do.
Screens also tend to cause eye strain.
Even if you do make pages responsive, chances are that the user will not realize that they should be using a skinny window or that they should shrink the text. Further, commercial web publications tend to optimize for maximized windows to display ads.
In print, we have hundreds of years of professional readability and layout experience. On the web we have some cobbled together standards. Most people who are responsible for handling web design aren't layout/typography/etc. specialists. So really basic mistakes get made all the time and few people notice them because our knowledge base has effectively eroded because there are so many other priorities to worry about on the web.
