Esports' biggest issue is that the only real reason someone is going to start watching is because they play the game and want to see pros play it. Esports are usually not much fun to watch if you don't already love the game (neither are traditional sports).
The main reason to watch a sport is because you love the game on one hand, or you love the teams/players on the other. Traditional sports get a lot of the latter because there's history and inertia.
You don't have to love football to cheer for the Pats when you live in Boston. But you aren't going to cheer for the Boston Uprising (or even be aware that they exist) if you don't love Overwatch.