It's pointless but harmless hobby. At 19 he could use his money for a lot worse things. He could also use them better, but why?
The idea that personal finances should always be optimised for the best possible future outcome is sickening to me. What's the point in that grind? To eventually have more money for ... more pointless hobbies? If so, then he already won the game by being able to enjoy a pointless hobby at the age of 19.
It's a good time to do it too. It's only getting more difficult and less enjoyable the older you get. Life shouldn't be so serious. Let the kids play as long as they can. People get mentally old because they stop playing.