Professional gaming is actually a fairly large industry. Not just E-Sports teams (CS:GO competitions and the like), but also gaming youtubers. The Yogscast, a youtube (group?) that started off doing WoW and Minecraft have now raked in almost 9 million pounds in 2016, and have 6.7m GBP in assets and 5.9m GBP in equity.
I mean those are pretty good numbers for what is essentially an office full of people playing video games.
Even PewDiePie, who made his fame screaming at trending games, or games that he made trending, has had multi million dollar salaries from his 55+ million subscribers, the most on the platform.