I'm pretty sure Microsoft's VHD file format has built-in support for sparse volumes... maybe it was a case of since they didn't need it, they could trim everyone else's advantage.

Since ReFS doesn't look to be in the client version of Windows 8, though, i don't think it'll make much difference to applications - and i expect they'll add some of these features back before Windows 9. Hopefully they have a more transparent versioning system than NTFS this time around