Snapchat is immensely more popular than Facebook for anyone under 25. They change and iterate their UI/UX quite often to confuse (keep away) adults from using it and "ruining" it for the younger audience.
Does anyone have a by country breakdown of snapchat users and growth? In Chile in my kids circle of friends, they used it a bit last year but have all deleted it now in favor of musically. Everyone here (kids and adults) also have whatsapp and I think the value of snapchat is even further diminished now that whatsapp is starting to clone some of the features.
