Why people don't done a OS in the floppy like MenuetOS !!!! if you can, help me !

Haiku (the open-source BeOS clone) can boot/run a console-based shell and apps from a floppy. A fully graphical BeOS will never be able to fit on a floppy though.

There are too many pieces. Consider all of the kits, libraries, the app_server, the tracker, and all of the apps and drivers that come with it. Meneuet doesn't even come close to the functionality of BeOS. For what it offers, BeOS is fairly small. (The pro edition takes well under 250MB of space, including GCC, BeIDE, all of the apps, drivers, and GoBE Productive 2.x)

There was (and if you look hard enough, you can still find it) something called BeIA, which was a cut down version of BeOS. Compressed, I think it took just 5-10MB. So it's still bigger than a floppy.