I think the success of Snapchat and shareable design is all about emotion. The moment when showing another how to do something on the phone, along with the close proximity, can likely trigger warm, positive feelings. Not only does this warm feeling help solidify the learning of a new feature, it also deepens the positive association the user has with the app. People remember how they feel and this contributes to app’s addictive quality.
Being spoken to softly, personal attention and learning are listed as triggers of ASMR (a pleasant tingling sensation). But even if the feeling does not lead to tingles, there is still a positive feeling derived from being taught something. (I’m sure there is an evolutionary component here…the caveman that felt good learning how to tie a rock to a stick must have had better chance of survival.)
Other emotions that come to mind from learning hidden features may be feelings of belonging, status, and even tribal. So while it’s not intuitive that a non-intuitive app like Snapchat would have such wild success, I attribute it to the power of emotion, and the addictive feelings that are triggered, and it starts to make a lot of sense.