Not saying I would object to more ports, just my guess as to why.
The enterprise people have already figured this out, I don't know why the consumer people haven't.
Also, I think most consumers who have a need for more than 4 computers to connect to their router via Ethernet probably don't want their entire network to have such an expensive single point of failure. I've had Ethernet ports on wireless routers die before. I like my switch separate from my router/AP separate from my modem.