Just because you don't know anyone that uses Snapchat doesn't make that an authoritative source on popularity of a company. Snap's user base has grown consistently and show's no signs of slowing down, even against increase competition in the space (https://www.statista.com/statistics/545967/snapchat-app-dau/). TikTok is the "Vine replacement" since Vine was bought by Twitter and shutdown. Vine wasn't a "fad" that faded away, it was actively shutdown by its parent company, likely would still exist to this day in a non-insignificant way had that not happen.