Are you asking why anyone needs an RTOS? It provides a very robust solution that sits somewhere between running a plain old OS like Linux and running baremetal C on a microprocesser. You get the speed benefit of baremetal but also get a scheduler and a whole bunch of multiprocessing structure to run lots of applications at once without worrying about manually switching or trying to create a massive main.c to do everything. VxWorks specifically runs on lots of industrial computers such that tasks can get done in a timely manner with little overhead.

VxWorks powers the Mars Rovers Sojourner, Spirit, Opportunity, Curiosity, Mars Reconnaissance Orbiter, and SpaceX Dragon. VxWorks also powers BMW iDrive, the Apache Longbow helicopter, and the Apple Airport Extreme and Linksys WRT54G routers. It's in a lot of things and what it's not in, FreeRTOS is probably the RTOS of choice.

One of the reason to buy VxWorks is that it comes with certification for various industries :

https://www.windriver.com/products/vxworks/certification-pro...

So if you have to explain to the regulatory body that you have a certified OS with all the appropriate paperwork, it always easier than certifying your custom OS.

The second point from an enterprise point of view is that in case of weird issue you can rely on Windriver support. Not so easy when you have built your own Yocto distribution, with recipe from dubious origin.

So in the end, you pay to mitigate risks.

My company investigated switching from VxWorks to Xenomai (wich helpfully provide a wrapper to access the kernel with a VxWorks compatible API). In the end, once you added the support and certification, it was not less expensive.

You are developing a medial, automotive, or aerospace application that needs hard real-time response rates and certification. There is also the option of paying a company to develop a BSP for your custom hardware rather than having to do it in-house. Another product in the same class is INTEGRITY from Green Hill Software.