Because it is more trouble than factory EFI, with no reallakotastoy said:
advantage over factory EFI!
I don't know how the Projection could be that much easier to trouble shoot than Ford EFI... a cheapo code scanner, fuel pressure tester, a couple of relays, and a spare TFI and you are set for most trailside problems. The whole point of EFI is so you don't have to screw with it! If I wanted to fiddle around to make the motor run right I'd save money and run a Holley carb. Factory EFI simply works right off the bat, no messing around. The big advantage with the factory EFI is there is ALOT of performance support for it so if you do want to upgrade there's plenty of stuff out there to do it with.