I'm quite sure that there are some software that is impossible to run on Wine. Drivers and other stuff that touches the kernel comes to mind.
And ReactOS does make Wine better as they share some code:
"ReactOS works with the WINE project to share as much programming effort as possible. ReactOS depends on Wine mainly for user mode DLLs. Where appropriate, patches to Wine are also submitted by the development team, and patch contributors are often directed to Wine if it is felt that the patches would benefit them." <http://www.reactos.org/wiki/WINE>;
I remember having read about the ReactOS/Wine cooperation, but I completely forgot about it while making my comment.
Still, it's not the kernel side of the driver that requires a bare OS, but the hardware side that requires the OS not to interfere. The foreign kernel can be emulated. A Windows-like OS can help you use hardware that has no drivers for other OSs but I never had this issue, nor know anyone who needs to run legacy hardware that can't also run a legacy OS.
And ReactOS does make Wine better as they share some code:
"ReactOS works with the WINE project to share as much programming effort as possible. ReactOS depends on Wine mainly for user mode DLLs. Where appropriate, patches to Wine are also submitted by the development team, and patch contributors are often directed to Wine if it is felt that the patches would benefit them." <http://www.reactos.org/wiki/WINE>;