As someone in their mid-twenties, I can confirm. Since a lot of users don't have iPhone's/iMessage, and/or just don't use Facebook/Messenger that much, it's become a go-to messaging platform for those that don't seek out the more dedicated ones like Whatsapp, at least in my non-technical circles. I'm in several group chats that all organically cultivated on Snapchat in the past couple years.

Besides that, they've built out their first-party content platform pretty well, which I assume is what's driving their advertising growth, and (anecdotally) is shared in-app relatively frequently, although I've recognized some reposting/reformatting of said video content from Youtube or other sources, e.g. WatchMojo.