On an ATX motherboard, SFP cages would impede into the space normally taken up by VRMs, their heatsinks, and the CPU socket. For a built in NIC, on consumer boa

On an ATX motherboard, SFP cages would impede into the space normally taken up by VRMs, their heatsinks, and the CPU socket. For a built in NIC, on consumer boards, an RJ45 port takes up way less space, no more than the USB ports and WiFi card does at the back of the board.