So I use netrunner most of the time, rolling to be exact, and theres the kernel screen to install kernels yeah? What are the real time kernels even for? Simulations? If so why are they channeled to normal users?
It is for real-time data such as live video, audio or other sensor data for controlling physical machines.
There are actually a lot of RT kernel applications. For instance, broadcast or studio boards and the entire DFX outboard runs on RT linux operation systems. It basically makes a full CPU based system behave like an MCU, like as if it were an arduino. The response is immediate, real-time. Also manufacturing chain robots in factories, which depend on sensory data and programmed decision making at the same time, in applications that are too complex or have too many variables for MCU's, run on CPU base computer systems with RT linux distros.
One of the most popular everywhere is SuSE RTOS. SuSE provides all of the kernel maintained by the project as RT kernels, and provides full RTOS ISO's for a preconfigured easy install.
I run a RT kernel right now, as that is what ships with Ubuntu Studio (in fact, was one of the main features of that flavor for some time). Anyway, that used to be pretty important when I used it for broadcasting my college radio station to keep everything as close to live as possible.
So, as mentioned, things that really use it a lot that I've had to use: audio, video and other broadcast software. Jack has an option to use Real TIme features if available (on my previous rig that was super slow, this ended up making things unusable as packets had to be dropped nearly constantly, and thus it demonstrated pretty quickly I needed something better than that if I wanted to do serious live radio broadcasting again).