I feel like to Twitter, Snapchat is more like Instagram. It may have more users but not the same effect. How useful is it[Snapchat]? Do you use it? Why?
The article: http://www.bloomberg.com/news/articles/2016-06-02/snapchat-passes-twitter-in-daily-usage
There's no need to document unimportant things. If you have a random thought that'd you like to blurt out to the world, there's Twitter. If you want to remain social with people outside of real life contact, there's Facebook. If you want to communicate with people, there are any number of messaging apps -- which, by the way, can send any form of media. If there's something going on that is interesting enough to where you'd want to document it semi-permanently, there's any number of cameras and camera apps. If you want to broadcast everything you're doing, there's Periscope and Facebook Live.
So the reason people -- particularly young people -- prefer Snapchat (outside the infamous sexting) is because they can essentially broadcast mildly noteworthy moments of their lives to their friends without worrying about all those pictures and movies hanging around, taking up space, or possibly coming back to embarrass them.
But as for me? My toddler just loves playing with the animated filters. That is literally the only reason I have it.
I use it for the ease of communication and the ability to share moments instantly. Sometimes I'll even use as a camera app.