I agree about childhood days, but I don't know if that's entirely it.
I think we now take technology for granted and apps/sites are less special of a thing than BBSs were. Users are fickle, so much is fad-based, and we move on to the next thing without a strong feeling towards the last. Using Snapchat isn't a primary hobby or thing that you devote time to, more of a thing you do while doing some other primary thing. If that makes sense. :)
I doubt that memories of Snapchat will be as strong to a user as memories of BBSs. But who knows.