If the argument is that this saves on network hardware costs, then you'd think ISPs would have some incentive to invest in decentralization as well. But I'm no

If the argument is that this saves on network hardware costs, then you'd think ISPs would have some incentive to invest in decentralization as well. But I'm not so sure about the thesis that it's just a software issue. It seems wasteful to sling electrons through a backbone and back when those bits are (physically) close by, but the cost here is not the distance those bits traveled, but the marginal cost of the physical hardware to deliver those bits to your doorstep. It's probably much cheaper, on a cost-per-bandwidth basis, to beef up the existing backbone, because significant economies of scale exist. OTOH, there's a significant fixed cost every time you try to widen edge links (it's very expensive to dig up and replace residential cables).