It's hard to blame PC vendors, considering that (x86) Windows wouldn't boot from EFI until 2008, and, even then, only with 64-bit CPUs. There is admittedly a little bit of a chicken-and-egg problem there, but Microsoft already had EFI code, since it booted Windows from EFI on Itanium, and PC vendors would have had to develop both an EFI firmware and a BIOS shim for it, to gain virtually no benefit.