Twitter has professionals and many people over the age of 18, so the user base is much different. Facebook is the same. My Mom and Dad are both on Facebook. If you notice, Facebook started becoming profitable when the moved outside of Universities.
Snapchat is mostly students and teenagers. I'm 38 and neither I nor any of my friends have ever used Snapchat (Most wouldn't even know what it is and I only know because I'm interested in Startups).
My point is that if you have no chance of moving outside of the student/teenager demographic with an app like this, it will be very difficult to monetize.
This has all of the chance in the world to move out of its current demographic, it'll just take time.