They do have that, it is called multiple 8-pin. There are cards that take 3. No reason to combine them as then you would run into the case of needing only an 8-pin and having a 16pin connector. Either every card would have to make room (the opposite of what they want) or the cable would need be splitable, which they already are...I wonder why they do not have a 16 pin PCIE connector as standard now. Aka join 2 PCIE8 for compatibility, do double for high power cards.. still compatible, etc..etc..
EPS does better because it carries an additional 12V wire vs the 3 of the 8-pin. Also already an existing standard used in the server space. Plenty of fanless GPUs that use a single EPS cable in datacenters.