You obviously have never had to transfer huge video files across a network from one Mac to another or needed to interact with a hard drive on another Mac on the network as if it was local.
Without GB Ethernet it takes TEN TIMES as long and other computers on teh net will NEVER feel local. If you don't need it fine. But I have needed it for years and would NEVER consider buying a computer without GB Ethernet. Even the lowly Mac mini has GB Ethernet now. It's really the only way to go if you use a network or even heve to hook up to a network for file sharing and transfers.
The difference between 100 Base T and 1000 Base T Ethernet is RADICAL. This is my view in a wired world. If you never connect to another computer, then you are right.