It could be that ATT is already charging consumers the maximum, or close to it, amount consumers will bear. In that case even with gigabit speeds the average consumer probably won't pay much more than their already paying. So, in the absence of competition to motivate them to improve their network they would have to find other revenue streams to justify the cost of installing a fiber-optic network. If they can't charge content providers to use a new faster network (or find some other way to increase their revue) then ATT won't want to build them.
