i think the main reason is that 99% of users, even most businesses, dont require more than 1Gb... Yea, if you are moving massive amounts of data around, 10Gb is handy, but 99 times out of 10, 1Gb will do. And its a chicken/egg situation. Since most people don't necessarily need it, manufactures wont make them in bulk... With the advent of larger games and faster consoles, maybe going to 10Gb will happen soon...

I do see 2.5 GbE NICs really making huge headway just within the past few years alone. Even lower end AMD and Intel motherboards are including 2.5 GbE ethernet ports by default these days, and that standard has the advantage of using the same copper RJ45 cabling, while giving you a theoretical 2.5x gain in speeds. For many users, even including myself, 2.5 GbE is a fantastic leap forward without having to dump money into fancier gear in order to properly take advantage of something faster like 10 GbE networking.