Linux already has a great marketshare - Android - but no perceptible effect on society, most people dont still know what Linux is, and certainly not what freedom in software is about. Which sucks, but thats the way it is, and once that changes, then we're in for great times.
1.) It's not open source
2.) They want to charge for certain features that are free in surespot.
(on top of the $100k they're already asking for)
3.) They wont let you run your own server
For an encryption app? I'd almost argue that not being able to access the source code makes it a non starter. There's no way to guarantee a lack of backdoors otherwise.