Does it really matter? Macs use EFI and Apple's selling them in record numbers.
Besides, the computer industry is undergoing a transition to web services and mobile hardware. What's the iPad using? That's what matters.
But if we're going to stick to what remains of the "traditional" computer market, then the problem is that legacyware is widespread, almost exclusively on the Windows/PC side.
32-bit architecture and hardly any support with PC manufacturers and vendors.
EFI is available for everything from Linux, HP OpenVMS, to Apple Intel, to certain 64-bit editions of Windows.
Unfortunately, due to the lack of support with PC manufacturers and vendors of 32-bit cpus and architectures, EFI support isn't available for 32-Bit processors. You won't see EFI become the standard until all of the new computers coming out (desktops, laptops, netbooks) are all 64-bit architecture (processors and motherboards). What's holding EFI back is not transitioning fully to 64-bit across the board and making a break with the past. The transition has slowly begun, however. It'll take some time.