RTOS versus RT application

We must distinguish between the application and the OS:

an RTOS is a tool that must provide absolute real-time behavior, or else it cannot be used to build real-time applications. An RTOS by itself is not enough to build a real-time system, but it allows the use of deterministic functions to produce an appropriate response time.
an RT application is built on top of an RTOS but may or may not show real-time behavior.

There are good cases for using an RTOS, even though the application does not require real-timeliness. Examples can be found in embedded systems where configurability of the OS may be a reason to choose an RTOS.

With INtime, a reason for choosing it in a non-RT application could be the improved reliability of the system.