I suspect that the design of the pedal itself and the bear-trap mechanism of it, i.e. the thin cages/arcs would wear down real quick if the cleats were of the same metal - it's in their documentation too, at least they say that the pedal lasts longer because of the softer cleats.

Admittedly, I liked them when I had them, they felt buttery-smooth but I got hot spots on them (undoubtedly because my Gekos probably have a lot less stiffness since I walk in them everywhere and use them day to day as regular shoes too). I also had trouble unclipping in the 12 o'clock position causing me to turn the heel inward in that position instead as opposed to outward which is where I usually clip out and in an emergency situation I didn't want to have to think about what came natural to me.