Issue with 10GbE is more just up front cost, there was no feasible path to make it mainstream through mass manufacture because the cost of the early "mainstream" devices would make/(has made) it incredibly niche anyway, 2.5GbE and 5GbE were developed together to bridge the gap so we can actually see something viable for inclusion on standard home routers and motherboards in the meantime, with 5GbE sharing cable requirements with 10GbE (Cat6 or better) to aid in the transition, and 2.5GbE a little "instantly usable" stop gap while we move to 5GbE+.