Yeah! obviously phaser is used for developing HTML 5 games. So, by the question i mean what are the opportunities that you get by developing HTML 5 games. Is there any way to sell the game or host it somewhere to earn revenues . fb is instant Game is one of such platforms but are there others too?? What are the benefits of learning it or say what are you utilizing the learned knowledge (of phaser game development)??
You can publish your games to Google Play and the App Store earn with Ads or offer In-App Purchases. (using capacitor)
You could also sell your game on Steam. (using electron)
JavaScript is great, since it works everywhere on any device.