Personally, I doubt if there is the "market" to really make it worth it from the manufacturer's position. Look how many more iPhones there are versus any model of camera flash. Dave's point about not using flash frequently also cements the notion of this: what manufacturer want's to make a state-of-the-art flash with all the bells and whistles with all the newest battery technology only to have the batteries go bad due to lack of proper care and feeding by the user? That manufacturer get's the blame for producing the most horrible flash ever made.......better to let the user screw with battery care, and not have Nikon or Canon blamed......

Those of us nursing Metz flashes of old with the old Ni-cd rechargeables know about battery care and nursing......rechargeable batteries of any technology do require care.....some more than others. There are some wonderful types of newer batteries out there that could almost live through our infrequent flash usage, but cost would be or could be significant so our camera manufactures will never consider producing them. So we are stuck with AA's for a long, long time.

Bob E.