Agreed! That was also one of the original goals of WinFS in Longhorn, but I wonder if it was just too early. The original problem with WinFS is that it was too slow, but that was before SSDs and several Moore doublings ago.
BeOS feels more like a document database - no defined schema, just attributes attached to your files.
I recall installing the WinFS beta 1 release and suddenly the winfs-related background processes were eating up 150MB+ of RAM at a minimum, even with no stores created or files indexed - when machines back in 2005 had 512MB of memory that's actually a lot for what is supposed to be a background service.
Windows XP back then only needed 128MB of ram to run. they made a mistake in not building it on top of something akin to sqlite - hell they could've implemented maybe 70% of what they shipped in beta 1 with just sqlite alone.