Look at YouTube’s largest channel in terms of number of subscriber. Eliminating VEVO channels, and YouTube’s own curation channels, #1 is PewDiePie, the famous/infamous Youtuber whose videos are mostly about him playing games, with his reactions recorded. Love it or loathe it, he is indeed the king of YouTube with over 40 million subscribers. But if you look down the list, most of the channels are gaming related.
YouTube recently launched YouTube Gaming, a mobile app/site dedicated to games and livestreams of games, to compete with Twitch, the de-facto leader in livestreams service for games- so successful Amazon bought them for almost a billion dollars. This implies both YouTube and Twitch are doubling down efforts on attracting gamers, which now represents a lot of their use base.
All of this huge boom of numbers spawned from the culture of watching videos of others playing games, otherwise known as Let’s Plays.