PoE is on one hand (relatively, for ~$10 devices) expensive to do, with all the signaling and filtering needed, while on the other hand, not abundant in the environments where these projects are run.
I do have an 8-port-1Gb/s-switch with 4-PoE ports at home. It cost 5 times as much as the "plain" 8-port-1Gb/s with no PoE, and I'm the only person I know who has one at home.
Oh definitely. "Real" PoE is expensive and unhelpful but it doesn't have to be standard PoE. You can just steal some pairs from cat5 and still get some form of ethernet. There are even cheap splitters/injectors out there. You won't get the nifty auto-negotiation, filtering, or anything else but it'll work.
I do have an 8-port-1Gb/s-switch with 4-PoE ports at home. It cost 5 times as much as the "plain" 8-port-1Gb/s with no PoE, and I'm the only person I know who has one at home.