The assumption that gaming is somehow less educational/social/healthy behaviour than, say, reading a book.
I saw 'PC gaming' mentioned as a category in a study about worrying teenage behaviours the other day. Other categorys were: Alcoholism, hard drug abuse, smoking, unprotected sex, and internet/social media addiction. The study showed a considerable regression in alcohol- and drugabuse as well as smoking in teens in favor of girls more heavily using social media and boys turning to PC gaming.
Now, my reaction to that would have been: while responsible use of social media is important and should be tought it is awesome that people would rather play games than take drugs. They thought the trend was worrying.