The problem with 2.5G is that it's not enough of an upgrade over 1G to warrant buying all new switches and NICs to get it. For that matter few home users push around enough data for 10G to be a big win.

IMHO this is why Ethernet has stalled out at 1G. People still don't have large enough data needs to make it worthwhile. See also: the average storage capacity of new personal computers. It has been stuck around 1TB for ages. Hell, it went down for several years during the SSD transition.