Though we see humongous enterprise applications; a single user uses only a small fraction of available features and functionalities. In fact he doesn’t want to see any other features cluttering his small smartphone screen. These limited interactions can be externalized in the form of mobile apps- each having a minimal UI to suit the user’s specific requirements.
Another reason why this evolution will happen is the speed at which technology and markets are developing. Things are changing so fast that there is no point building big products that take a year or more to release. It’s best to avoid the risk of obsolescence by releasing small apps at short intervals.