It's the social aspect and the act of "dude there's a Snorlax at the basketball court let's go" and getting a group of your friends to go, then as you show up you see other people doing the same thing.

It's an innocent conversation starter. What better ice-breaker between social groups than "You playing Pokemon?" Even people who aren't playing know what's going on. The game itself isn't the selling point here. Being an IRL Pokemon trainer is.

Everyone now with a smartphone can Pokémon game for free! This captures the previous market who grew out of it. Furthermore AR works very well with the Pokémon theme.