Mike Bates:

It sounds odd, but the best parts of playing Pokémon GO happen when you’re not touching the phone. It’s a little tough to summarize, but I think I’d group those best-experiences into exploring, spending time with friends, and meeting new people while out and about.

I haven’t had much time to play Pokémon Go myself, but from everything I’ve seen on Twitter, this is the perfect way to explain it’s popularity.