·Verizon Online DSL
Easy: it's cheaper to upgrade ten households to 8x4 D3 than it is to serve one with new coax/fiber. So only the visionary providers (NOT AT&T/Verizon...these days/Frontier/Windstream/etc.) are doing that outside of greenfield developments, which aren't going up like they used to.
This is from someone whose parents are limited to 1.5/384 DSL (at least it's reliable!) and who has one choice for more than 5 Mbps down and 700 kbps up at his apartment right next to school (10 Gbps pipe, 1 Gbps between buildings, 100 Mbps Ethernet to most PCs, gigabit to a few): Comcast.