One of the reason to buy VxWorks is that it comes with certification for various industries : https://www.windriver.com/products/vxworks/certification-profiles

One of the reason to buy VxWorks is that it comes with certification for various industries : https://www.windriver.com/products/vxworks/certification-profiles/ 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.