If you think of an OS as solely something that sits on your desktop, then sure, but this is fairly myopic (and defeatist). There are lots of small, proprietary

If you think of an OS as solely something that sits on your desktop, then sure, but this is fairly myopic (and defeatist). There are lots of small, proprietary and often embedded operating systems that rely on the same principles established by present and past OS. Writing operating systems is also a great way/introduction to work on operating systems, and it's a fairly distinct area of development. It's hard to get day-to-day overlap if you're working on things that don't have the constraints and operating system does.