Comcast, and effectively all US broadband providers, are massively underprovisioned for the quantity of service they've sold, because that was a good way to make a lot of money and because, until very recently, it was quite difficult for residential customers to actually use enough bandwidth for the underprovisioning to pose an issue. Now, with the advent of 4k streaming and similar popular consumer services that actually do require significant bandwidth, it's not surprising to see this sort of activity as a means of avoiding the need to provision backhaul equal to the promises these companies have made.