I don't get why my kids watch the ish they do on youtube including watching others play video games, but if they're happy and not hurting themselves or anyone else and otherwise productive, fine. I'm sure my parents thought the same of 13 year old me doing whatever I was doing (eg, playing video games, beating it like there's no tomorrow, listening to "devil" music and gangsta rap), and I like to think I turned out just fine.
To each their own... follow the interest and follow the money. Move on with the times or you'll be left behind.
But if the argument is about what makes something a sport... does it need to be athletic, involve precision, be competitive... I don't know and honestly, I don't care. Get out there and have fun doing what you like to do even if it's just watching other people play games.