Writing an OS from scratch is hard work, and without complying with pre-existing standards, the new OS won't be able to take advantage of existing software or communicate with computers running different operating systems, making it a non-starter for most users. Even supporting a wide range of hardware is very challenging, especially given the fact that many hardware devices lack documentation sufficient to write drivers, which results in challenging reverse-engineering projects or relying on the hardware manufacturer to create drivers for the new OS; this is a challenge even for Linux, which has the best driver support outside of Windows. Most people who want to experiment with new ideas for computer systems end up building on top of Linux since they can leverage Linux's existing hardware support and its implementation of a wide range of standards allowing interoperability.

I'm working on an experimental desktop computing project that ironically uses Plan 9 as its base platform since Plan 9's everything-is-a-file interface and its overall simplicity allows me to build my project with less effort than dealing with Linux/X11/Wayland/dbus/etc., but a big part of me is tempted to eventually write some 9P services to emulate enough of the underlying Plan 9 architecture to run my project on Linux and the BSDs in order to take advantage of these operating systems' better driver support.