Whilst the OP is after ostensibly practical examples, I would add something I haven't yet seen mentioned and that is education. If you are wanting to learn more

Whilst the OP is after ostensibly practical examples, I would add something I haven't yet seen mentioned and that is education. If you are wanting to learn more about computing and how operating systems work, Linux is excellent at giving you this opportunity. It actually takes one of it's weaknesses and turns it into one of it's biggest strengths. Because you often need to tinker a bit with scripts and problem-solving in order to get certain things working the way you want, you learn a lot. For example, when I was into gaming in my younger years I was lucky to have access to a family computer rather than a gaming console. Because of this, I gained experience tinkering with config.sys and autoexec.bat in order to make my games run on limited memory, and later, learning how to add hardware like 3D accelerators for faster performance. If I had been stuck with a static console without any room for modification, I may have taken a less interesting career path as a result. I feel a similar lamentation when seeing kids with iPads, but feel hope when I see them tinkering with Minecraft :)