A way to continue to run XP, while providing user experience with OS X. A migration path. It would, perhaps, be hard limited in the amount of RAM it would support.
Apple wont do it cause they dont own Parallel, and because they are growing their Mac sales without doing it.
My wife works for herself and is locked into XP. Many of the programs she uses are not complaint with the newer operating systems. We looked into this and to upgrade the OS would require a $5K investment in new software and we would gain no new functionality. I’m sure many other firms are facing this same situation.
And on the external hard drive is a reference/clean copy of the XP VM, ready to copy over to the main hard drive if for any reason the main VM gets corrupted, or I want to revert to an earlier time (e.g. before a test install of an application).
Parallels does approximately the same stuff, a little cheaper than VMware.
I don't see any reason why Apple would do anything like that, given that they already have BootCamp. BTW, VMware can also treat the BootCamp partition as a VM during OS-X operation. I don't know if Parallels will do that.