The architecture of NoSQL makes it a good choice for big data solutions while the built in protections of a transactional based system like Oracle make it a better choice for banking or similar solutions.
When it comes to picking a specific system, businesses tend to stick with what they know. In other words, if they already have Oracle, and Oracle talent, then when management asks those individuals which database system they should use on Project X, it should be no surprise that they pick Oracle.