I'd guess external IO (memory and PCIe) might be a problem. How are you going to route all those wires out from the socket? Secondly, there's probably some eco

I'd guess external IO (memory and PCIe) might be a problem. How are you going to route all those wires out from the socket? Secondly, there's probably some economic argument as well. Too few customers willing to pay for a humongous MCM, and with the attendant wiring complexity requiring more layers for the motherboard, it might be cheaper to go to more sockets instead?